Extend X11 response parsing

Add support to parse screens, depths, visual-types and
pixel-formats in the X11 connection initial response.

v1->v2:
- Do not show unused bytes when their length is 0
- Fix up tabs

Change-Id: If62f0eab65a18e050fb3f830a6bd7574ab1f2de6
Reviewed-on: https://code.wireshark.org/review/4249
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>