Fix lazy evaluation of second argument to append-pipes for consistency with make-pipe; fixes mappend-pipe laziness

Ignore-this: f3fed201712877e374d820d195f79ce1

darcs-hash:fbc7a09b8d36e224a278b21b6b374442e835edc1

darcs-hash:45334d1ba300293b9a7377fd0ebabaee1019e7e5

"oops"

darcs-hash:124414697b6eca4a749814989db32489946b1315

Fixed xnum parsing / unparsing.
Fixed comparison operators.
Added lang() function.
Node sets returned by EVALUATE and EVALUATE-COMPILED now are automatically sorted
using document order by default.
Fixed following:: axis (again).
Fixed NODE-TEST-NAME for namespace nodes.
Numbers in XPath expressions are now never parsed into SINGLE-FLOAT.
Added SORT-NODE-SET function.

darcs-hash:f11136c9917dee6bd41d96f3e8950db389c78b55

darcs-hash:cbeecb1a3180fb0663c8e9f9cae929339ddc16a4

darcs-hash:d40b75c09b911dc74c448e12734de19df206bb38

darcs-hash:d3828b9c30d4ea787fb181678a3db979fbd16f09

darcs-hash:f28b33b1e2da78f194b265817967068d0d49fd2a

functions.lisp
        - new function XPATH:UNION for the | operator
          (not a keyword because not technically an XPath function)

lexer.lisp
	Lots of fixes.

node-tests.lisp
	- NODE-TEST-NAME
	  Added the namespace URI as an optional second argument.
	- NODE-TEST-NAMESPACE
	  New, checks only the namespace and not the local name.
	- NODE-TEST-PROCESSING-INSTRUCTION
	  Added the name to check as an optional argument.

types.lisp
	- CONTEXT-VARIABLE-VALUE
	  New generic function looking up variable values during
	  evaluation.
	- ENVIRONMENT
	  New struct, basically a compilation-time context.
	- ENVIRONMENT-FIND-NAMESPACE
	  New generic function for prefix -> uri lookups
	- ENVIRONMENT-FIND-FUNCTION
	  New generic function for (local-name uri) -> function lookups.
	- ENVIRONMENT-VALIDATE-VARIABLE
	  New generic function that returns true if the variable is
	  declared.
	- TEST-ENVIRONMENT
	  An environment that pretends to know about every namespace,
	  function, and variable. For use only in parser tests.

xpath.lisp

	- MAKE-LOCATION-STEP
	  Now accepts the list of predicates instead of just one
	  predicate.
	- COMPILE-PREDICATES
	  helper function for make-location-step
 	- DECODE-QNAME, FIND-NAMESPACE
	  New
	- COMPILE-XPATH
	    * New second argument `environment'.
	    * For function calls, check if the function name is a string
	      rather than a symbol, and if so, look it up in the enviroment.
	    * New: variables
	    * New: filters
	- COMPILE-VARIABLE
	  New
	- COMPILE-NODE-TEST
	  Split qnames.  And allow lists as node-tests to handle
	  :namespace, named :processing-instruction, and pre-parsed :qname
	- COMPILE-LOCATION-STEP
	    * New second argument `environment'.
	    * Accept multiple predicates.
	- COMPILE-PATH
	  New second argument `environment'.
	- COMPILE-FILTER-PATH
	  New

axis.lisp
	- new axis :namespace
	- new axis :following-sibling
	- new axis :preceding-sibling
	- new axis :following
	- new axis :preceding
	- new axis :ancestor-or-self
	and
	- pseudo axis :root  -- FIXME: is this right?

darcs-hash:828be75c0208ef166e480cfe33eb83b3ac57f285

darcs-hash:b96e13c8d54121d1fbfffc220ff442053e425942