Remove the so called hairy (semantic) parsers.

Remove the so called hairy (semantic) parsers.
* src/system.h (EXT_GUARD_C, EXT_STYPE_H): Remove.
* src/gram.h, src/gram.c (semantic_parser): Remove.
(rule_t): Remove the guard and guard_line members.
* src/lex.h (token_t): remove tok_guard.
* src/options.c (option_table): Remove %guard and %semantic_parser
support.
* src/output.c, src/output.h (guards_output): Remove.
(prepare): Adjust.
(token_definitions_output): Don't output the `T'
tokens (???).
(output_skeleton): Don't output the guards.
* src/files.c, src/files.c (attrsfile): Remove.
* src/reader.c (symbol_list): Remove the guard and guard_line
members.
Adjust dependencies.
(parse_guard): Remove.
* data/bison.hairy: Remove.
* doc/bison.texinfo (Environment Variables): Remove occurrences of
BISON_HAIRY.