Constify atom name strings

Changes MakeAtom to take a const char * and NameForAtom to return them,
since many callers pass pointers to constant strings stored in read-only
ELF sections.   Updates in-tree callers as necessary to clear const
mismatch warnings introduced by this change.

Signed-off-by: Alan Coopersmith <alan.coopersmith@sun.com>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>

include/xkbsrv.h

@@ -880,7 +880,7 @@ extern _X_EXPORT XkbGeometryPtr XkbLookupNamedGeometry(
 );
 
 extern _X_EXPORT char *	_XkbDupString(
-	char *			/* str */
+	const char *		/* str */
 );
 
 extern _X_EXPORT void	XkbConvertCase(