Multiplication of the matricies was being done in the wrong direction.
This caused source transformations to come out looking incorrect, for
example the linux-xshm source's cursor would not be drawn correctly or
in the right position if the source was moved/scaled/rotated. The
problem just turned out to be that the gs_matrix_* functions were
multiplying in the wrong direction. Reverse the direction of
multiplication, and the problem is solved.
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