Enable CHECK_UNHANDLED_OOPS for Windows fastdebug builds

For some platforms we do fastdebug builds with -DCHECK_UNHANDLED_OOPS. But Windows (and aix) are excluded from that: from JvmFlags.gmk:

    ifeq ($(call isTargetOs, windows aix), false)
        # NOTE: Old build did not define CHECK_UNHANDLED_OOPS on Windows and AIX.
        JVM_CFLAGS_DEBUGLEVEL += -DCHECK_UNHANDLED_OOPS
    endif

Of course, it might not currently build, and might not run if it does build. But it would be better to have this be consistent with other platforms.