This fixes https://github.com/kichikuou/xsystem4-android/issues/14.
There appears to be a bug in the OpenGL ES implementation for PowerVR
that prevents row_major mat4x3 uniforms from loading correctly.
This changes bone_matrices from row_major mat4x3 to column_major mat3x4
and transposes them manually in the vertex shaders. (Column major mat4x3
cannot be used due to the UBO size limitation)