Bug 1022049 - #include intrin.h directly instead of defining the intrinsics manually; r=froydnj
Disable bitscan intrinsics on clang-cl because it doesn't support #pragma intrinsic
Use the C/C++ compilers passed in through mozconfig in order to preprocess on Windows instead of hardcoding the usage of cl
Use the C/C++ compilers passed in through mozconfig in order to preprocess libffi on Windows instead of hardcoding the usage of cl
Revert "Use the C/C++ compilers passed in through mozconfig in order to preprocess libffi on Windows instead of hardcoding the usage of cl"

This reverts commit 0ac4a4e14b4a0fa896daa35f6e30fc90559042b9.