Adding a .ycm_extra_conf file for webkitGtk

https://bugs.webkit.org/show_bug.cgi?id=119618

Patch by Martin Robinson  <mrobinson@igalia.com> and Danilo Cesar Lemes de Paula <danilo.cesar@collabora.co.uk> on 2013-12-11
Reviewed by Gustavo Noronha Silva.

Added a YouCompleteMe flag discovery script for Vim and the GTK+ port. The script
read the GTK+ build files to determine dynamically what flags to compile a source
file with. This allows Vim to provide auto-complete for C++/C language. See
https://github.com/Valloric/YouCompleteMe for how to use this file.

.:

* .gitignore: Ignore the YCM symlinks in the tree.

Tools:

* gtk/common.py:
(get_build_path): Added a fatal argument to build_path to avoid crashing YCM on failure.
* gtk/ycm_extra_conf.py: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160531 268f45cc-cd09-0410-ab3c-d52691b4dbfc