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/zeromq/zeromq.toml

@@ -0,0 +1,53 @@
+[build]
+type = "cmake"
+
+[build.flags]
+build_dir = "build"
+configure = [
+    "-DCMAKE_POLICY_VERSION_MINIMUM=3.5",
+    "-DBUILD_SHARED=ON",
+    "-DBUILD_STATIC=OFF",
+    "-DENABLE_CPACK=OFF",
+    "-DZMQ_BUILD_TESTS=ON",
+    "-DWITH_OPENPGM=ON",
+    "-DOPENPGM_PKGCONFIG_NAME=openpgm-5.3",
+    "-DWITH_LIBBSD=ON",
+    "-DWITH_LIBSODIUM=ON",
+    "-DENABLE_CURVE=ON",
+    "-DWITH_DOC=ON",
+    "-G Ninja",
+    "-Wno-dev",
+    "-DCMAKE_CXX_STANDARD=11",
+    '-DCMAKE_CXX_FLAGS="-Drestrict=__restrict__"'
+]
+
+[dependencies]
+build = [
+    "cmake",
+    "ninja",
+]
+optional = ["cppzmq"]
+runtime = [
+    "glibc",
+    "gnutls",
+    "util-linux",
+    "libsodium",
+    "libpgm",
+    "libcxx",
+    "libunwind",
+]
+
+[package]
+description = "Fast messaging system built on sockets. C and C++ bindings. aka 0MQ, ZMQ."
+homepage = "http://www.zeromq.org/"
+license = "MPL-2.0"
+name = "zeromq"
+version = "4.3.5"
+
+[[source]]
+extract_dir = "$name-$version"
+url = "https://github.com/zeromq/libzmq#v$version"
+patches = [ "fix-doc-install.patch" ]
+
+[[manual_sources]]
+file = "fix-doc-install.patch"