Move class temp_source_file from input.c to selftest.c/h

Move class temp_source_file from input.c to selftest.c/h

gcc/ChangeLog:
	* input.c (class selftest::temp_source_file): Move to
	selftest.h.
	(selftest::temp_source_file::temp_source_file): Move to
	selftest.c.
	(selftest::temp_source_file::~temp_source_file): Likewise.
	* selftest.c (selftest::temp_source_file::temp_source_file): Move
	here from input.c.
	(selftest::temp_source_file::~temp_source_file): Likewise.
	* selftest.h (class selftest::temp_source_file): Move here from
	input.c

From-SVN: r239509