Use Cairo for wxGraphicsContext in wxX11.

Check for Cairo in configure for wxX11 too.

Fix compilation of wxCairoContext for non-{GTK,MSW} platforms.

Also make wxUSE_CAIRO a "normal" option, i.e. add it to all wx/setup.h files
instead of defining it as 1 unconditionally for wxGTK and 0 for everything
else.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66094 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/univ/setup0.h

@@ -688,6 +688,19 @@
 #   define wxUSE_GRAPHICS_CONTEXT 0
 #endif
 
+// Enable wxGraphicsContext implementation using Cairo library.
+//
+// This is not needed under Windows and detected automatically by configure
+// under other systems, however you may set this to 1 manually if you installed
+// Cairo under Windows yourself and prefer to use it instead the native GDI+
+// implementation.
+//
+// Default is 0
+//
+// Recommended setting: 0
+#define wxUSE_CAIRO 0
+
+
 // ----------------------------------------------------------------------------
 // Individual GUI controls
 // ----------------------------------------------------------------------------