Add method expand-to-foreign-dyn-indirect for type foreign-type-alias so that foreign-string-type will be expanded correctly (as a pointer).

* Instead of a special variable, the parsed struct type instance is now
  annotated to let the type system know whether we're dealing with
  deprecated semantics (struct type canonicalizes to :pointer) or not.

  This approach should hopefully be much less error-prone.

* Disabled translations for bare structs.

* Fixed and commented out some bogus tests.

Create a new function #'foreign-expand-runtime-translator-or-binding
which is what the methods
  expand-to-foreign-dyn (value var body (type enhanced-foreign-type))
  expand-to-foreign-dyn-indirect (value var body (type translatable-foreign-type))
both call.  Previously, the body of that function was the body of the
first method, and the second method called that generic function.
This did not work as intended however, the result being that libffi
calls were passed the actual object instead of the pointer.  This
change fixes that problem.

New function expand-to-foreign-dyn-indirect split out from
expand-to-foreign-dyn, and the latter function returned to its
definition as given in the tip of master, ab10be4f.  This function
is used if the optional argument 'indirect to translate-objects is T,
which in turn the case when functions are calling or return structures
by value.

Use hash table for libffi-type-pointer instead of a class slot, and
simplify #'libffi-type-pointer methods.  Remove obsolete package
definition file.  Tests in cffi-tests not run due to error in load,
but GSLL tests pass.

Argument 'indirect to #'expand-to-foreign-dyn is key instead of
optional, so that other systems that define a method can just have
&key, and they do not have to add this argument if they don't need to
use it.

In order that structures called by value work correctly (in
cffi-fsbv), add methods:
translate-into-foreign-memory 
  foreign-built-in-type
  enhanced-typedef
expand-to-foreign-dyn
  foreign-built-in-type
  foreign-pointer-type

The generic function translate-into-foreign-memory has been slightly
repurposed and expanded to provide indirection of enums and pointers.
The function translate-objects and generic function
expand-to-foreign-dyn have a new argument, 'indirect, that when set,
expand to with-foreign-object and translate-into-foreign-memory
instead of translate-to-foreign, unwind-protect, and
free-translated-object.  This insures that all arguments to functions
passed to libffi are indirected one level, as is required.

Add :argument-precedence-order to defgenerics
translate-into-foreign-memory and translate-to-foreign, and removed
the 'cons specializer in the tests.

Add respective struct tests, one of which fails. Also, missing union
tests.

:STRUCT and :UNION types live one their own namespaces (as in C) and this
supported by FIND-TYPE-PARSER itself. (Although one has to manually
implement parse methods for each namespace, as we did for :STRUCT and
:UNION.)

Bare FOO references are parsed to (:STRUCT foo) or (:POINTER (:STRUCT foo))
depending on context and signal a style warning about their deprecation.

Note that CANONICALIZE now returns a list like (:STRUCT/:UNION foo) for
struct/union types instead of always returning a keyword denoting a
built-in type.

Unions now have their own FOREIGN-UNION-TYPE, a subclass of
FOREIGN-STRUCT-TYPE.

1. Idea: Make a slot for libffi-type-pointer and define for all
built-in types, then define methods to make the pointer on demand for
other type classes.
2. Add slot [libffi-type-pointer] with generic function to defclass
foreign-type. 
3. New file [built-in-types.lisp] defines all built-in types, and
libffi-type-pointer :around method for typedefs/aliases.
4. New [libffi-type-pointer :around method] for foreign-struct-type.
5. New lists exported from CFFI for possible other uses, and needed
here: *other-builtin-types* *built-in-integer-types*
*built-in-float-types*.

Created a function cstruct-libffi-type-pointer that generates the
libffi-type structure for any foreign structure type, so that this
structure may be used as an argument or return call by value to a
foreign function.  It replaces the automatic generation of this
structure when defstruct is compiled or loaded (via
*defcstruct-hook*), so that it is only made when needed and cffi-fsbv
need not be loaded when the defcstruct is compiled.  The structure
will only be made once; it is bound to the plist of the type symbol
(as before), and is reused if needed again.  This function compiles
but has not yet been tested.

Said expansion breaks the protocol between TRANSLATE-TO-FOREIGN and
FREE-TRANSLATED-OBJECT.

This wasn't an issue when using EXPAND-TO-FOREIGN-DYN since it discards
the default expansion of EXPAND-TO-FOREIGN. Only CONVERT-OBJECT-FOREIGN
and DEFCALLBACK call EXPAND-TO-FOREIGN directly and the latter has to
discard the second value anyway.

Implemented a new generic function TRANSLATE-AGGREGATE-TO-FOREIGN to
support (SETF FOREIGN-SLOT-VALUE) for aggregate slots.

Don't need to check for cycles (which starts off by consing up
a hash table) when not dealing with foreign-typedefs. Initial
patch courtesy of Greg Pfeil.

Patch courtesy of Douglas Crosher.

Bug reported by Attila Lendvai.

The changes are summarized here:
http://article.gmane.org/gmane.lisp.cffi.devel/1029

Also adapted tests and examples and uffi-compat.

Three new features:
  - stdcall (defcfun, foreign-funcall(-pointer), defcallback)
  - namespaces, associate foreigns vars and functions to a
    specific library. (CLISP and Lispworks only)
  - close-foreign-library actually works now.

Backwards incompatible changes:
  - define-foreign-library's syntax changed slightly, can't
    load more than one foreign library per define-foreign-library
    form anymore.
  - defcvar's syntax changed.
  - foreign-funcall can't funcall pointers anymore. Use
    foreign-funcall-pointer for that.

- :POINTER without arguments is a void pointer.
- (:POINTER :INT) is a pointer to an :INT.
- These nest properly: (:POINTER (:POINTER :INT)).
- Pointers are not type checked yet---an optional pointer type checker
  will be added someday.

- Remove *runtime-translator-form* from the public interface, in favor
  of (call-next-method).
- Describe this change in the manual, including some text from the
  option 1 patch.
- Be clear that ALLOC-PARAM is thrown out by %expand-type-to-foreign.

- change expand-type-to-foreign-dyn for foreign-typedef to not
  short-circuit expand-type-to-foreign when falling back (see paste
  17379)
- add tests showing that you can change the foreign-dyn expansion
  semantics by providing an expand-to-foreign method that falls back

- bugfix, foreign-alloc doesn't need to call translate-type-to-foreign
  explicitly since mem-aref already does. Bug reported by Greg Pfeil.
- new keyword argument: NULL-TERMINATE-P.
- new regression tests for the bug described above and new tests for
  the new keyword argument.
- document new argument.