* cpphash.h (struct cpp_buffer): Delete read_ahead and extra_char.
	* cpplex.c (lex_percent, lex_dot): Remove.
	(get_effective_char, skip_block_comment, skip_line_comment,
	parse_identifier_slow, parse_number, parse_string, save_comment,
	_cpp_lex_direct): Update to do lookback freely.
	(IF_NEXT_IS, BACKUP): New macros.
	* cpplib.c (cpp_push_buffer): Don't set read_ahead and extra_char.
	* cppmacro.c (paste_tokens): Update.

From-SVN: r46392