Blitter int to int copy fix

Integer to integer types copy operations were failing due
to a missing assignment when calling the Insert function
and bad offsets on 16 and 32 bit component types.

Change-Id: I2db55e9b6a284f8349e8fef0451255ee33be5837
Reviewed-on: https://swiftshader-review.googlesource.com/4410
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>