Named symbol references.

Discussed in:
http://lists.gnu.org/archive/html/bison-patches/2009-01/msg00000.html
http://lists.gnu.org/archive/html/bison-patches/2009-02/msg00002.html
http://lists.gnu.org/archive/html/bison-patches/2009-03/msg00009.html

	* src/parse-gram.y: Add new syntax (named_ref.opt).
	* src/reader.c: Store named refs in symbol lists.
	* src/reader.h: New argument for symbol_append and
	action_append functions.
	* src/scan-code.h: Add new field (named_ref) into
	code_props data structure. Keeps named ref of midrule
	actions.
	* src/scan-code.l: Support for named refs in semantic
	action code. New function 'parse_named_ref'.
	* src/scan-gram.l: Support bracketed id.
	* src/symlist.c: Store named refs in symbol lists.
	* src/symlist.h: New field in symbol list: named_ref.
	* src/named-ref.h: New file, a struct for named_ref.
	* src/named-ref.c: New file, named_ref_new function.
	* src/Makefile.am: Add two new files.
	* tests/testsuite.at: Include new test group:
	* tests/named-refs.at: this new file.

src/Makefile.am

@@ -67,7 +67,8 @@ bison_SOURCES =					  \
 	system.h				  \
 	tables.h tables.c			  \
 	uniqstr.c uniqstr.h			  \
-	graphviz.c graphviz.h
+	graphviz.c graphviz.h			  \
+	named-ref.c named-ref.h
 
 EXTRA_bison_SOURCES = scan-code.l scan-skel.l scan-gram.l