This returns a population count of all the bits that are set in the
bitmask.
There is now also a _cogl_bitmask_popcount_upto which counts the
number of bits set up to but not including the given bit index. This
will be useful to determine the number of uniform overrides to skip if
we tightly pack the values in an array.
The test-bitmask test has been modified to check these two functions.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
f23b12a886