[OpenMP][Doc] Update release note for 16 release

Author: shiltian

openmp/docs/ReleaseNotes.rst

@@ -20,27 +20,40 @@ from the `LLVM releases web site <https://llvm.org/releases/>`_.
 Non-comprehensive list of changes in this release
 =================================================
 
+* OpenMP target offloading will no longer support on 32-bit Linux systems.
+  ``libomptarget`` and plugins will not be built on 32-bit systems.
+
 * Support for building the OpenMP runtime for Windows on AArch64 and ARM
   with MinGW based toolchains.
 
 * Made the OpenMP runtime tests run successfully on Windows.
 
-* Improved performance and internalization when compiling in LTO mode using 
+* Improved performance and internalization when compiling in LTO mode using
   ``-foffload-lto``.
 
-* Created the ``nvptx-arch`` and ``amdgpu-arch`` tools to query the user's 
+* Created the ``nvptx-arch`` and ``amdgpu-arch`` tools to query the user's
   installed GPUs.
 
-* Removed ``CLANG_OPENMP_NVPTX_DEFAULT_ARCH`` in favor of using the new 
+* Removed ``CLANG_OPENMP_NVPTX_DEFAULT_ARCH`` in favor of using the new
   ``nvptx-arch`` tool.
 
-* Added support for ``--offload-arch=native`` which queries the user's locally 
-  available GPU architectures. Now ``-fopenmp --offload-arch=native`` is 
+* Added support for ``--offload-arch=native`` which queries the user's locally
+  available GPU architectures. Now ``-fopenmp --offload-arch=native`` is
   sufficient to target all of the user's GPUs.
 
-* Added ``-fopenmp-target-jit`` to enable JIT support.
+* Added ``-fopenmp-target-jit`` to enable JIT support. Only basic JIT feature is
+  supported in this release. A couple of JIT related environment variables were
+  added, which can be found on `LLVM/OpenMP runtimes page <https://openmp.llvm.org/design/Runtimes.html#libomptarget-jit-opt-level>`.
 
-* OpenMP now supports ``-Xarch_host`` to control sending compiler arguments only 
+* OpenMP now supports ``-Xarch_host`` to control sending compiler arguments only
   to the host compilation.
 
 * Improved ``clang-format`` when used on OpenMP offloading applications.
+
+* ``f16`` suffix is supported when compiling OpenMP programs if the target
+  supports it.
+
+* Python 3 is required to run OpenMP LIT tests now.
+
+* Fixed a number of bugs and regressions.
+