Replace void with int to make this a valid C++ file.

The test was passing because clang would still print the ast before exiting
with an error. Since that didn't seem to be the intent of the test, I change
the test instead of adding 'not' to the command line.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185634 91177308-0d34-0410-b5e6-96231b3b80d8