* cpplex.c (IS_HSPACE, S_NEWLINE): Remove.
(IS_DIRECTIVE): Rename KNOWN_DIRECTIVE.
(skip_block_comment, skip_line_comment, parse_string,
lex_line): Use is_vspace rather than IS_NEWLINE.
(skip_whitespace, lex_line): Clean up to use is_nvspace.
(lex_line): Use KNOWN_DIRECTIVE. Any kind of directive
gets a BOL flag.
(lex_next): Unconditionally stop if within a directive.
Treat directives within macro invocations as directives
(after parse_args emits error), not as the argument.
* testsuite/gcc.dg/cpp/directiv.c: New tests.
* testsuite/gcc.dg/cpp/undef1.c: Update.