Add PIXMAN_x8b8g8r8 and PIXMAN_a8b8g8r8 formats to scaling-test

Add PIXMAN_x8b8g8r8 and PIXMAN_a8b8g8r8 formats to scaling-test

Update the CRC values based on what the general implementation
reports. This reveals a bug in the fast implementation:

    % env PIXMAN_DISABLE="mmx sse2" ./test/scaling-test
    pixman: Disabled mmx implementation
    pixman: Disabled sse2 implementation
    scaling test failed! (checksum=AA722B06, expected 03A23E0C)

vs.

    % env PIXMAN_DISABLE="mmx sse2 fast" ./test/scaling-test
    pixman: Disabled fast implementation
    pixman: Disabled mmx implementation
    pixman: Disabled sse2 implementation
    scaling test passed (checksum=03A23E0C)

Reviewed-by: Matt Turner <mattst88@gmail.com>