Fixing a compile error that recently started happening for me in MSVC 2013....

Fixing a compile error that recently started happening for me in MSVC 2013. CFGTerminator has an explicit conversion to bool operator that we can make use of instead of using == 0.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198175 91177308-0d34-0410-b5e6-96231b3b80d8