Remove remnants of OpenWebRTC

Remove remnants of OpenWebRTC
https://bugs.webkit.org/show_bug.cgi?id=178437

Reviewed by Alejandro G. Castro.

.:

Remove the FindOpenWebRTC.cmake file and the searches for it in both
OptionsGTK and OptionsWPE.

* Source/cmake/FindOpenWebRTC.cmake: Removed.
* Source/cmake/OptionsGTK.cmake:
* Source/cmake/OptionsWPE.cmake:

Tools:

Drop OpenWebRTC packages from the GTK's Jhbuild modules file. Relevant
patches are also removed.

* gtk/jhbuild.modules:
* gtk/patches/libnice-0001-TURN-allow-REALM-to-be-empty.patch: Removed.
* gtk/patches/libnice-0001-nicesrc-spin-the-agent-mainloop-in-a-separate-thread.patch: Removed.
* gtk/patches/rtspsrc-timeout-on-udpsrc-is-in-nanoseconds.patch: Removed.
* gtk/patches/udpsrc-improve-timeouts.patch: Removed.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@223601 268f45cc-cd09-0410-ab3c-d52691b4dbfc