- Fix :LICENSE -> :LICENCE in cffi-grovel.asd
- grovel.lisp fixes:
    * fix OpenMCL's INVOKE
    * have INVOKE call NATIVE-NAMESTRING
    * add IGNORABLE declaration to DEFINE-GROVEL-SYNTAX
- CMUCL's EXT:UNIX-NAMESTRING is buggy, don't use it.
- strings.lisp: pass missing max-octets argument to OCTET-COUNTER
  in FOREIGN-STRING-ALLOC.

Added a groveller based on Dan Knap's and Matthew Backes's cffi-grovel
and Stelian Ionescu's fork iolib-grovel.  cffi-grovel is inspired by
SBCL's groveller.  This is a preliminary version.

Includes a new wrapper generator syntax to simplify the writing of
C glue libraries among other minor features.

- Updated TODO items related to grovelling.
- Integrated documentation into the CFFI manual.
- src/libraries: use ".so" as the default library suffix.