PEDANTIC defaults to ON and WERROR default to off.
Also add MSVC warnings. To disable warnings add the flags
LLVM_ENABLE_WARNINGS (default on).
Patch by Tobias Grosser!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90188 91177308-0d34-0410-b5e6-96231b3b80d8