Drivers need this if they add visuals that require implicit redirection. Add a
new SDK header, compositeext.h, to contain the prototype for this function.
The composite overlay window code had several misunderstandings of the
workings of the X server, in particular error handling paths would often
double-free objects. Clean all of this up by using resource destruction as
the sole mechanism for freeing resource-based objects.
Get rid of almost all uses of these definitions. They're still defined for
delinquent out-of-tree drivers, and also for the Mesa build. As well as
for miinitext.c. But largely gone.