gdb

	* parser-defs.h (parser_debug): Declare.
	* parse.c (_initialize_parse): Install "debug parser" set/show
	command.
	(parser_debug): New global.
	(show_parserdebug): New function.
	* c-exp.y (c_parse): Set yydebug.
gdb/testsuite
	* gdb.texinfo (Debugging Output): Document set debug parser and
	show debug parser.