by verifying intltool-update exists. If not, then fail cmake more cleanly
with a nice error message telling the user how to install it.
(LP: #1023742)
  
The truly weird part is that I've been building compiz successfully for a
long time without intltool-update installed. However we have some broken
cmake dependencies somewhere which *sometimes* make that a problem (like
with make -j2), but mostly not a problem (like make -j1).