This adds a test which tries manipulating some bits on a CoglBitmask
and verifies that it gets the expected result. This test is fairly
unusual in that it is directly testing some internal Cogl code that
isn't exposed through the public API. To make this work it directly
includes the source for CoglBitmask.
CoglBitmask does some somewhat dodgy things with converting longs to
pointers and back so it makes sense to have a test case to verify that
this is working on all platforms.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
