[Development] Updating the minimal supported version of libxcb

[Welbourne Edward]

Alexander said:
> Qt officially supports the following platforms that use libxcb:
> OpenSuSE 13.1 (libxcb 1.9.1, xcb-proto 1.8)
> Red Hat Enterprise Linux 6.6 (libxcb 1.9, xcb-proto 1.8)
> Ubuntu 14.04 - 64bit (libxcb 1.10, xcb-proto 1.10)

For reference, Debian stable (Jessie) is also on 1.10

    Eddy.