This patch implements FRAMEBUFFER_INCOMPLETE_MULTISAMPLE checking for
checkFramebufferStatus, and also modify conditions of
FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENTS when setting default
parameters to fbo.

BUG=angleproject:1594
TEST=angle_end2end_tests --gtest_filter=FramebufferTest_ES31*
TEST=dEQP-GLES31.functional.texture.multisample.negative.fbo_attach_different_fixed_state_tex*

Change-Id: I86954056d3a5d89dca517b267bd16e17b70e5652
Reviewed-on: https://chromium-review.googlesource.com/437991
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>