[Xcb] [PATCH:libX11] Don't need to link libX11-xcb against libX11

[Josh Triplett]

On Fri, Nov 15, 2013 at 06:03:25PM -0800, Alan Coopersmith wrote:
> libX11-xcb only accesses data structures defined in X11 headers,
> it doesn't call any functions or reference any global variables
> in libX11 itself.  (Seems to have been left from previous XCL
> implementation.)
> 
> Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>

That's not the only reason for this dependency.  As you said, libX11-xcb
accesses data structures defined in libX11 headers.  In particular, it
relies on the newly added "xcb" field in Display.  Without a dependency
on libX11, it would be possible for an application to link with
libX11-xcb and with an older version of libX11 that does not have the
"xcb" field (and doesn't use libxcb underneath).

- Josh Triplett