The new MOZ_ASSERT_CLASSNAME check in MOZ_COUNT_CTOR and friends
fails under gcc 4.4 on the B2G ICS emulator build, because
nsGonkCameraControl calls the COUNT macros from a local class.
This wasn't allowed in C++03, but that was changed in C++11, and
our more recent toolchains either don't reject the code or don't
encounter such a nested class name.
I picked gcc 4.7 as the minimum version because that's the version
used by the B2G JB Emulator build, which works. There's no restriction
on clang or msvc version.
3f1557189d