Add a hack for compiling xcb/xcb_icccm.h with C++.

xcb/xcb_iccm.h isn't C++ safe (some versions) because it has
a variable called "class" in function signatures. The hack
is to define "class" to something else before that header is
included, and then undef "class" immediately afterwards.

CCMAIL: mgraesslin@kde.org, fredrik@kde.org

xcbutils.h

@@ -29,7 +29,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <xcb/xcb.h>
 #include <xcb/composite.h>
+#define class class_name //HACK: work around a non-C++ safe problem in xcb_iccm.h
+                         //where they put a variable called "class" in function signatures.
+                         //Needed at least for xcb v0.3.8
 #include <xcb/xcb_icccm.h>
+#undef class             //UNDO HACK
 
 namespace KWin {