Enable WebGL on Windows CMake build.

Enable WebGL on Windows CMake build.
https://bugs.webkit.org/show_bug.cgi?id=143311

Reviewed by Csaba Osztrogonác.

.:

* Source/cmake/OptionsWindows.cmake:
Enable WebGL by default in CMake builds now that it works.

Source/ThirdParty/ANGLE:

* CMakeLists.txt: Added.

Source/WebCore:

* CMakeLists.txt:
ANGLE is built quite differently on Windows, so I'm not going to touch the existing CMake build system for
ANGLE on Linux, although I think it should eventually be unified more by using ANGLE's OpenGL renderer.
* PlatformWin.cmake:
Added some needed source files and include directories.

Source/WebKit:

* PlatformWin.cmake:
Added some needed source files and include directories.

Source/WTF:

* wtf/FeatureDefines.h:
Made the CMake feature defines the same as the non-CMake feature defines.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@187866 268f45cc-cd09-0410-ab3c-d52691b4dbfc