package/x11r7/xcb-util-renderutil: new package

[Thomas:
  - rewrap Config.in help text
  - add missing depends on BR2_PACKAGE_LIBXCB]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>