re PR preprocessor/77699 (suspicious code in get_next_line)

2016-10-03  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        PR preprocessor/77699
        * input.c (maybe_grow): Don't allocate one byte extra headroom.
        (get_next_line): Return false on error.
        (read_next_line): Removed, use get_next_line instead.
        (read_line_num): Don't copy the line.
        (location_get_source_line): Don't use static data.
        (selftest::test_reading_source_line): Add more test cases.

From-SVN: r240713