rs6000: Parsing built-in input file, part 1 of 3

rs6000: Parsing built-in input file, part 1 of 3

2021-07-20  Bill Schmidt  <wschmidt@linux.ibm.com>

gcc/
	* config/rs6000/rs6000-gen-builtins.c (bif_stanza): New enum.
	(curr_bif_stanza): New variable.
	(stanza_entry): New struct.
	(stanza_map): New initialized variable.
	(enable_string): Likewise.
	(fnkinds): New enum.
	(typelist): New struct.
	(attrinfo): Likewise.
	(MAXRESTROPNDS): New macro.
	(prototype): New struct.
	(MAXBIFS): New macro.
	(bifdata): New struct.
	(bifs): New variable.
	(curr_bif): Likewise.
	(bif_order): Likewise.
	(bif_index): Likewise.
	(fatal): New function.
	(stanza_name_to_stanza): Likewise.
	(parse_bif_attrs): New stub function.
	(parse_prototype): Likewise.
	(parse_bif_entry): New function.
	(parse_bif_stanza): Likewise.
	(parse_bif): Implement.
	(set_bif_order): New function.
	(create_bif_order): Implement.