Add new packages and build scripts for various libraries

- Added Nuklear GUI library with build script and configuration.
- Introduced OpenH264 encoder/decoder with build configuration.
- Added PortAudio library for audio I/O with custom build script.
- Included Python Execnet for multi-Python deployment.
- Added Pytest Xdist plugin for distributed testing.
- Introduced Shaderc for shader compilation tools.
- Added Snappy compression library with necessary patches and configuration.
- Included SoundTouch audio processing library with build configuration.
- Added SRT library for secure reliable transport.
- Introduced VapourSynth video processing framework with configuration.
- Added Vid.stab for video stabilization.
- Included WebRTC Audio Processing library with build configuration.
- Added X264 video encoding library with patches for POSIX compliance.
- Introduced X265 video encoder with build configuration.
- Added XKeyboard Config for X keyboard configuration files.
- Included Xorg XKBComp for keyboard description compilation.
- Added Xvidcore MPEG-4 video codec library with configuration.
- Introduced ZeroMQ messaging system with patches and build configuration.
- Added Zimg library for scaling and colorspace conversion.

extra/jack2/jack2-1.9.22-db-5.3.patch

@@ -0,0 +1,15 @@
+diff --git i/wscript w/wscript
+index 86eb3954..bdd29dc3 100644
+--- i/wscript
++++ w/wscript
+@@ -199,8 +199,8 @@ def options(opt):
+     db = opt.add_auto_option(
+             'db',
+             help='Use Berkeley DB (metadata)')
+-    db.check(header_name='db.h')
+-    db.check(lib='db')
++    db.check(header_name='db5.3/db.h')
++    db.check(lib='db-5.3')
+ 
+     # dbus options
+     opt.recurse('dbus')