When RandR 1.2's transformation code is enabled, it rotates the cursor
image so that it appears upright on a rotated screen.  This code
completely mangles 2-color cursors on hardware where the the mask and
source images are not interleaved due to two problems:

1. stride is calculated as (width / 4) rather than (width / 8), so the
   expression (y * stride) skips two lines instead of one for every
   time y is incremented.
2. cursor_bitpos ignores the 'mask' parameter if the hardware doesn't
   specify any of the HARDWARE_CURSOR_SOURCE_MASK_INTERLEAVE_* flags.

To fix this, refactor the code to pass the whole xf86CursorInfoPtr
through to cursor_bitpos and compute the correct stride there based on
the flags.  If none of the SOURCE_MASK_INTERLEAVE flags are set, use
the total cursor size to move the 'image' variable into the mask part
of the image before computing the desired byte pointer.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Robert Morell <rmorell@nvidia.com>
Reviewed-by: Alex Deucher <alexdeucher@gmail.com>
Tested-by: Cyril Brulebois <kibi@debian.org>