[GTK] [CMake] Add a "make dist" target

[GTK] [CMake] Add a "make dist" target
https://bugs.webkit.org/show_bug.cgi?id=116378

Reviewed by Gustavo Noronha Silva.

.:

* Source/PlatformGTK.cmake: A CMake support for executing the make-dist
script and then turning the tarfile into a LZMA compressed file.

Source/WebCore:

* CMakeLists.txt: Don't build WebKitVersion.h for WebKitGTK+. We don't use it
and we don't want to distribute the dependency.

Tools:

Added a script that reads a manifest file an produces a tarball. Also add
the manifest.

* gtk/make-dist.py: Added.
* gtk/manifest.txt: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@163114 268f45cc-cd09-0410-ab3c-d52691b4dbfc