* cpplex.c (_cpp_lex_token): Handle directives in macro
	arguments.
	* cpplib.c (_cpp_handle_directive): Save and restore state
	if parsing macro args when entering a directive.
	* cppmacro.c (collect_args): No need to handle directives
	in macro arguments.
	(enter_macro_context, replace_args): Use the original macro
	definition in case it was redefined whilst collecting arguments.
doc:
	* cpp.texi: Update.
testsuite:
	* gcc.dg/cpp/undef1.c: Remove.
	* gcc.dg/cpp/directiv.c: Update.
	* gcc.dg/cpp/mac-dir-1.c, mac-dir-2.c: New tests.

From-SVN: r50091