* gengtype-parse.c: New file.
	* gengtype-yacc.y: Delete.
	* gengtype-lex.l: Don't include gengtype-yacc.h.
	Define YY_DECL and yyterminate appropriately for recursive
	descent parser.  yylval is now a string out-parameter to yylex.
	(HWS, EOID): New shorthand.
	(IWORD): Add a couple more types.
	(yylex): Add a setup stanza.  Remove the complex rules for
	detecting GTY'ed types and typedefs; replace with simple
	keyword detectors.  Adjust everything for the changed
	definition of yylval.  Ignore all pp-directives, not just #define.
	(yyerror): Delete.
	(parse_file): Rename yybegin; do not call yyparse.
	(yyend): New.
	* gengtype.c (xasprintf): Export again.
	(this_file): New.  Use everywhere __FILE__ was being used.
	(get_lang_bitmap): Special case types defined in gengtype.c.
	(do_typedef, new_structure): Suppress definition of certain types.
	(new_structure): Improve diagnostics of duplicate definitions.
	Make sure location_s is associated with input.h.
	(nreverse_pairs, define_location_structures): New functions.
	(main): Improve tagging of kludge types.  Remove old kludges
	for input.h types; use define_location_structures.
	* gengtype.h: Update prototypes.  Define token codes here.
	* Makefile.in: Remove all references to gengtype-yacc.
	Add rules for gengtype-parse.o.  Adjust rules for gengtype-lex.o
	and gengtype.
	* bitmap.h (struct bitmap_head_def): Coalesce definitions,
	add GTY((skip)) to the field that's only conditionally there.
	* doc/install.texi: Document that Bison is no longer required
	unless building treelang.

From-SVN: r123235