Rename xDepth to xPDepth to quiet -Wshadow warnings

Xrender.c: In function ‘XRenderQueryFormats’:
Xrender.c:406:19: warning: declaration of ‘xDepth’ shadows a global declaration [-Wshadow]
     xPictDepth   *xDepth;
                   ^~~~~~
In file included from /net/also.us.oracle.com/export/alanc/X.Org/amd64-gcc/install/usr/X11R7/include/X11/Xlibint.h:43:0,
                 from Xrenderint.h:31,
                 from Xrender.c:28:
/net/also.us.oracle.com/export/alanc/X.Org/amd64-gcc/install/usr/X11R7/include/X11/Xproto.h:329:7: note: shadowed declaration is here
     } xDepth;
       ^~~~~~

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
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