[Preprocessor] Always discard body of #define if we failed to parse it
Preivously we would only discard it if we failed to parse parameter lists.
If we do not consume the body, parser sees tokens inside directive. In
turn, this leads to spurious diagnostics and a crash in TokenBuffer, see
the added tests.
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D65517