Remove CPP_PLACEMARKERs

Remove CPP_PLACEMARKERs

	* cppexp.c (lex): Don't handle CPP_PLACEMARKER.
	* cpplex.c (_cpp_lex_token): Rename skip_newlines to next_bol
	* cpplib.c (skip_rest_of_line, check_eol, cpp_push_buffer):
	           Similarly.
	* cpplib.h: Remove CPP_PLACEMARKER.
	(struct lexer_state): Rename skip_newlines to next_bol.
	* cppmacro.c (stringify_arg): Don't handle CPP_PLACEMARKER.
	Simplify prev_white handling as a result.
	(paste_all_tokens): Don't worry about CPP_PLACEMARKERs.
	(parse_arg): Empty arguments are now empty, not CPP_PLACEMARKERs.
	(parse_args): Similarly.  Update argument count tests.
	(enter_macro_context): Return 2 to indicate an empty macro.
	(replace_args): Don't bother pre-expanding an empty argument.
	Handle placemarkers and ## extension during pre-expansion.
	(cpp_get_token): Handle empty macro expansions.  Don't worry
	about CPP_PLACEMARKERs.
	(_cpp_create_definition): Empty macros are now empty.
	(cpp_macro_defintion): Don't special case empty macros.
	* scan-decls.c: Don't bother with CPP_PLACEMARKERs.
	* c-lex.c: Similarly.

From-SVN: r37385