libcpp: Fix ICE with directives-only and cpp_maybe_module_directive [PR124153]

When doing directives-only processing (-E -fdirectives-only, or -M) we
crash if we hit an unexpected CPP_PRAGMA_EOL because we 'know' we're in
a module directive but the in_deferred_pragma flag is no longer set.

Fixed by undoing the "finished a module directive" behaviour within
cpp_maybe_module_directive if we're bailing due to an ill-formed peeked
token.

	PR c++/124153

libcpp/ChangeLog:

	* lex.cc (cpp_maybe_module_directive): Set in_deferred_pragma
	and eol when we see an unexpected CPP_PRAGMA_EOL.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/cpp-22.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>