Add a lossy 32-bit generic pixel fetch function for wide surfaces.

Add a lossy 32-bit generic pixel fetch function for wide surfaces.

The transformed fetch path currently only works at 32-bit precision.  Until a
wide version of that function is added, we need to have a path to perform a
wide FetchPixel and then contract it down to a8r8g8b8.

Also, use the right format when expanding the result in fbFetchTransformed64.
fbFetchTransformed returns a8r8g8b8 results.