Add rotate-test.c test program

Add rotate-test.c test program

This program exercises a bug in pixman-image.c where "-1" and "1" were
used instead of the correct "- pixman_fixed_1" and "pixman_fixed_1".

With the fast implementation enabled:

     % ./rotate-test
     rotate test failed! (checksum=35A01AAB, expected 03A24D51)

Without it:

     % env PIXMAN_DISABLE=fast ./rotate-test
     pixman: Disabled fast implementation
     rotate test passed (checksum=03A24D51)

V2: The first version didn't have lcg_srand (testnum) in test_transform().