Add test to verify accuracy of multisample scaled blitting

Note: Test passes with all of the scaling factors between 0.1 to 2.5
on Intel's i965 drivers. Patches for scaled blitting support on i965
are out for review on mesa-dev mailing list.
Add test to verify the accuracy of multisample scaled blit using a shader program

Note: Test passes with all of the scaling factors between 0.1 to 2.5
on Intel's i965 drivers. Patches for scaled blitting support on i965
are out for review on mesa-dev mailing list.
Add test to verify the error conditions in ext_multisample_framebuffer_blit_scaled

Note: Test passes on Intel's i965 drivers. Patches for scaled
blitting support on i965 are out for review on mesa-dev mailing list.