b=520030 increase --enable-system-cairo required version to ensure fixes for @font-face crashes r=jdaggett

--HG--
extra : rebase_source : 63192b9609ccccdd153b66ab32ea8cd4f9050460

configure.in

@@ -121,7 +121,7 @@ GLIB_VERSION=1.2.0
 LIBIDL_VERSION=0.6.3
 PERL_VERSION=5.006
 PYTHON_VERSION=2.4
-CAIRO_VERSION=1.6.0
+CAIRO_VERSION=1.8.8
 PANGO_VERSION=1.14.0
 GTK2_VERSION=2.10.0
 WINDRES_VERSION=2.14.90