Support building angle with clang-cl

This works around http://llvm.org/PR20013.

Change-Id: Ibbd8ab4678cf1caf39b329ea304bdbdc21075ddf
Reviewed-on: https://chromium-review.googlesource.com/206481
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: <ehsan@mozilla.com>
Add ANGLE_NO_EXCEPTIONS macro

This macro allows us to hide angle's usage of try/catch so that we can
properly hide them from compilers that do not support exceptions
properly (such as clang-cl and gcc/clang with -fno-exceptions).

Change-Id: I75f466a5322e5840e007711ea851f444bd6ca299
Reviewed-on: https://chromium-review.googlesource.com/206562
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: <ehsan@mozilla.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Add Makefile.in (needed for moz tree for now)

Change-Id: Ib0093021a860afa2df699e1b7b24cccad41b2e35
Add gyp_mozbuild and associated build machinery for generating moz.build files

Change-Id: I05449681c021dc1e8fc9d618572c666aece99f54