[GTK] Add a basic cmake build for WTF and JavaScriptCore
https://bugs.webkit.org/show_bug.cgi?id=115967

Reviewed by Laszlo Gombos.

.:

* CMakeLists.txt: Add GTK+ to the list of ports.
* Source/CMakeLists.txt: We do not try to build WebCoreTestSupport when WebCore is disabled.
* Source/cmake/FindGAIL3.cmake: Added.
* Source/cmake/FindGDK3.cmake: Added.
* Source/cmake/FindGStreamer.cmake: Use the passed in minimum version.
* Source/cmake/FindGTK3.cmake: Added.
* Source/cmake/FindXt.cmake: Added.
* Source/cmake/OptionsEfl.cmake: Pass in the minimum version.
* Source/cmake/OptionsGTK.cmake: Added.

Source/JavaScriptCore:

* PlatformGTK.cmake: Added.
* shell/PlatformGTK.cmake: Added.

Source/WTF:

* wtf/PlatformGTK.cmake: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149968 268f45cc-cd09-0410-ab3c-d52691b4dbfc