This allows people to initialize a matrix with a translation
transformation. The options to do it at the moment were:
* init_from_array() but it give cogl no information about the type of
matrix.
* init_indentity() and then translate() but it means doing a lot of
computations for no reason.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 068b3b59221e405dc288d434b0008464684a7c12)
7ff0b52d78