illumos gate

Build errors with gcc compilers:

    diff.c: In function 'dump_context_vec':
    diff.c:1177:3: error: 'b' may be used uninitialized in this function [-Werror=maybe-uninitialized]
     1177 |   fetch(ixold, b+1, upb, 0, uflag ? " " : "  ", 1);
          |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    cc1: all warnings being treated as errors

    diff.c: In function 'dump_context_vec':
    diff.c:1221:3: error: 'd' may be used uninitialized in this function [-Werror=maybe-uninitialized]
       fetch(ixnew, d + 1, upd, 1, "  ", 0);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    cc1: all warnings being treated as errors
    *** Error code 1
    dmake: Fatal error: Command failed for target `diff'
    Current working directory /code/illumos-gate/usr/src/cmd/diff

Testing done: build/install/boot. Using diff command.