Fixed blitter operation from alphaless types
Fixed blitter operation from alphaless types

Some types without alpha were not correctly setting the
alpha value, so copying to a type with alpha was causing
the image to not appear (due to it being almost completely
transparent).

Change-Id: Ib12c291bd5c51628e0579285731033372656f6a0
Reviewed-on: https://swiftshader-review.googlesource.com/4391
Reviewed-by: Nicolas Capens <0612353e1fcebbfd4b302d9337447ca0cdfa9122@google.com>
Tested-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>

google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader