Revert r237766, "Support: Introduce LLVM_FALLTHROUGH macro."

The value of this macro seems to be very low unless we actually start
using it everywhere, and I don't have immediate plans to make that
happen.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237941 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed