[libcxx] [test] Fix MSVC warning C4067 "unexpected tokens following preprocessor directive - expected a newline".

Also fixes Clang/LLVM 4.0 (for Windows) error "function-like macro 'TEST_GLIBC_PREREQ' is not defined".

Fixes D34535.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@308533 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed