re PR preprocessor/39647 (Syntax checks in #line not quite right)

libcpp:
	PR preprocessor/39647
	* directives.c (check_eol): Add parameter expand.
	(do_undef, parse_include, do_line, do_linemarker, do_ident,
	do_pragma_once, do_pragma_system_header, do_ifdef, do_ifndef,
	do_else, do_endif, do_assert, do_unassert): All callers changed.
	Pass true from do_line, false elsewhere.

gcc/testsuite:
	* gcc.dg/cpp/line7.c: New test.

From-SVN: r146316