[GTK] Build ANGLE sources into a separate library from libWebCore.la

[GTK] Build ANGLE sources into a separate library from libWebCore.la
https://bugs.webkit.org/show_bug.cgi?id=112778

Reviewed by Martin Robinson.

.:

* GNUmakefile.am: Include the GNUmakefile.am covering the libANGLE.la library.

Source/ThirdParty/ANGLE:

* GNUmakefile.am: Added, sets up the libANGLE.la library.

Source/WebCore:

No new tests - no change in functionality.

* GNUmakefile.list.am: Remove the ANGLE sources listing, it's now placed in the ANGLE-specific GNUmakefile.am.

Source/WebKit/gtk:

* GNUmakefile.am: Add libLevelDB.la to the libwebkitgtk library if using the OpenGL accelerated backend.

Source/WebKit2:

* GNUmakefile.am: Add libLevelDB.la to the libwebkit2gtk library if using the OpenGL accelerated backend.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@146390 268f45cc-cd09-0410-ab3c-d52691b4dbfc