* egl.c (struct _EglBuffer): New field `scale'. Save the
projective scale here.
(struct _CompositeProgram): New field `scale'. Save the index
of new uniform here.
(EglCompileCompositeProgram): Fetch location of new uniform.
(ApplyTransform): Set scale.
(Composite): Apply value of new uniform.
(BufferFromDmaBuf, BufferFromShm): Initialize scale to 0.
(UpdateBufferForDamage): Scale damage if it and damage are set.
* shaders.txt (Composite Rectangle Fragment Shader RGBA)
(Composite Rectangle Fragment Shader RGBX)
(Composite Rectangle Fragment Shader External): New uniform
`scale'.
(main): Divide texcoord by scale.
