cppexp.c, [...]: Do not use 'legal' or 'illegal' in error messages and comments.

cppexp.c, [...]: Do not use 'legal' or 'illegal' in error messages and comments.

	* cppexp.c, cppinit.c, cpplex.c, cpplib.c, cppmacro.c,
	cppspec.c: Do not use 'legal' or 'illegal' in error messages
	and comments.

	* cppmain.c (cb_define, cb_undef): Don't generate any output
	if not done_initializing.
	* cpplex.c (maybe_paste_with_next): When the token after a ##
	is an omitted rest argument, only delete the token before it
	if that token is a comma.  Do not warn about bogus token
	pastes for , ## rest_arg.

	* cpp.texi: Update.
	* cpp.1: Regenerate.

	* gcc.dg/cpp/macsyntx.c: Fix error regexp.

From-SVN: r35421