[Win32] Catch exceptions (eg. segfault) on waiting for invoked clang from the driver.

clang/lib/Driver/Driver.cpp: Don't pass through negative exit status, or parent would be confused.

llvm::sys::Program::Wait(): Suppose 0x8000XXXX and 0xC000XXXX as abnormal exit code and pass it as negative value.

Win32 Exception Handler: Exit with ExceptionCode on an unhandle exception.

llvm-svn: 145389