[Xcb] build gdk on cairo-xcb

[Jianjun Yang - 杨建军]

hi, everybody

   i want to build gtk+ with xcb instead of xlib , here are my steps:
   step 1:   build cairo-1.0.2 , i use "--enable-xcb --disable-xlib" as the configure option.
   step 2:  build pango-1.10.0 , then i get libpangocairo,etc.
   step 3:  build gtk+-2.8.9 , but i met the following error:

In file included from gdkdrawable-x11.c:32:
/Helium/host/include/cairo/cairo-xlib.h:76:3: #error Cairo was not compiled with support for the xlib backend.

   i found that gdkdrawable-x11.c include cairo-xlib.h only. i think there should be conditional compile, just include cairo-xlib.h or cairo-xcb.h .
   is there gdkdrawable-x11.c that use cairo-xcb yet ? 


-jianjun