DeqAsyncHandler: add do ... while (0) to avoid -Wextra-semi-stmt warnings

Clears 12 warnings from clang of the form:

cmsCmap.c:194:34: warning: empty expression statement has no effect;
 remove unnecessary ';' to silence this warning [-Wextra-semi-stmt]
            DeqAsyncHandler(dpy, &async);
                                        ^

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Part-of: <!272>