mesa: add unpacking code for MESA_FORMAT_Z32_FLOAT_S8X24_UINT

Fixes glGetTexImage() when converting from MESA_FORMAT_Z32_FLOAT_S8X24_UINT
to GL_UNSIGNED_INT_24_8.  Hit by the piglit
ext_packed_depth_stencil-getteximage test.

Cc: "10.0" "10.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
(cherry picked from commit a12d4d0398c437911720069d293b469c60c4488c)
dri/i9*5: correctly calculate the amount of system memory

The variable name states megabytes, while we calculate the amount in
kilobytes. Correct this by dividing with the correct amount.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Cc: "10.0 10.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
(cherry picked from commit fc25956badb8e1932cc19d8c97b4be16e92dfc65)
mesa: Bump version to 10.1-rc3

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>