libXext: Multiple integer overflows leading to heap-based buffer-overflows

Multiple integer overflows in X.org libXext 1.3.1 and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XcupGetReservedColormapEntries, (2) XcupStoreColors, (3) XdbeGetVisualInfo, (4) XeviGetVisualInfo, (5) XShapeGetRectangles, and (6) XSyncListSystemCounters functions.