DRI2 fixes resend

[Kristian Høgsberg]

I'm resending the patch series to fix the XID confusion in DRI2.  Patches
2, 3 and 4 have already been review and/or tested, but the first patch
needs review again.  Patch 1 is the one that fixes the resource count
in dix/resource.c.  Keith pointed out that the other recent resource
functions also didn't maintain the count and that 
LookupClientResourceComplex() and FreeClientNeverRetainResources()
didn't check the count before and after doing their callback so as to
be reentrancy save.

I updated the patch to fix these issues, but now it's an even bigger
change to a subtle core subsystem that otherwise hasn't changed much
for a long time... in other words, please help review!

Kristian