* cppfiles.c (struct include_file): Move from cpphash.h.
        (_cpp_never_reread): New function.
        (open_file, read_include_file): Use it.
        (stack_include_file): Set the buffer's sysp according to the
        path in which the file was found.
        (find_include_file): Don't set sysp.
        (cpp_make_system_header, actual_directory): Update.
        (_cpp_execute_include): Do #include_next lookup handling here,
        not in cpplib.c.  Use _cpp_never_reread.
        * cpphash.h (struct_include_file): Remove.
        (struct cpp_buffer): New member sysp.
        (CPP_IN_SYSTEM_HEADER, _cpp_execute_include): Update.
        (_cpp_never_reread): New.
        * cpplib.c (read_line_number): Rename read_flag.  Rework slightly.
        (end_directive): Clear line_extension flag.
        (_cpp_handle_directive): Set line_extension flag for #number.
        (do_include_next): Handle path lookup in _cpp_execute_include.
        (do_line): Cleanup to use read_flag.  Don't allow flags in #line.
        (_cpp_do_file_change): Update.
        (do_pragma_once): Use cpp_never_reread.  Clean up.
        * cpplib.h (struct lexer_state): New member line_extension.

From-SVN: r38120