Implement -Wswitch-enum correctly.

Clang previously implemented -Wswitch-enum the same as -Wswitch. This patch
corrects the behavior to match GCC's. The critical/only difference being that
-Wswitch-enum is not silenced by the presence of a default case in the switch.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148679 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed