* cppexp.c (parse_defined): Always record the macro name.
	(lex): Don't worry about identifiers, or special-case
	CPP_NOT here.
	(_cpp_parse_expr): Figure out at the end of the routine
	whether we saw a valid !defined() expression.
	* cppfiles.c (stack_include_file): Update for mi_valid.
	(_cpp_pop_file_buffer): Similarly.
	* cpplex.c (_cpp_lex_token): Similarly.
	* cpphash.h (enum mi_state, enum mi_ind, mi_state,
	mi_if_not_defined, mi_lexed): Remove.
	(mi_valid): New.
	* cpplib.c (do_if): Simplify.
	(do_endif, push_conditional, _cpp_handle_directive): Update
	for renaming of mi_state to mi_valid.

	* cpp.texi: Add index entries for digraphs, and add comment
	that C++ refers to them as alternative tokens.

From-SVN: r44459