st/wgl: check for negative delta in wait_swap_interval()
This can happen because of rollover. See bug report for details. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102241 Cc: mesa-stable@lists.freedesktop.org Reviewed-by:Brian Paul <brianp@vmware.com> Reviewed-by:
Jose Fonseca <jfonseca@vmware.com> (cherry picked from commit d90e05ad)