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/snappy/snappy-reenable_rtti.patch

@@ -0,0 +1,25 @@
+diff --unified --recursive --text --new-file snappy-1.2.2.orig/CMakeLists.txt snappy-1.2.2/CMakeLists.txt
+--- snappy-1.2.2.orig/CMakeLists.txt	2025-04-19 23:20:48.985433149 +0200
++++ snappy-1.2.2/CMakeLists.txt	2025-04-19 23:20:27.703912696 +0200
+@@ -51,10 +51,6 @@
+   string(REGEX REPLACE "/EH[a-z]+" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHs-c-")
+   add_definitions(-D_HAS_EXCEPTIONS=0)
+-
+-  # Disable RTTI.
+-  string(REGEX REPLACE "/GR" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /GR-")
+ else(MSVC)
+   # Use -Wall for clang and gcc.
+   if(NOT CMAKE_CXX_FLAGS MATCHES "-Wall")
+@@ -81,10 +77,6 @@
+   # Disable C++ exceptions.
+   string(REGEX REPLACE "-fexceptions" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-exceptions")
+-
+-  # Disable RTTI.
+-  string(REGEX REPLACE "-frtti" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+ endif(MSVC)
+ 
+ # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to make