* 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.