[Docs] Release notes for OpenCL

Differential Revision: https://reviews.llvm.org/D51212



git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_70@340910 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Anastasia Stulova

docs/ReleaseNotes.rst

@@ -222,10 +222,31 @@ Objective-C Language Changes in Clang
 
 ...
 
-OpenCL C Language Changes in Clang
-----------------------------------
+OpenCL C/C++ Language Changes in Clang
+--------------------------------------
 
-...
+Miscellaneous changes in OpenCL C:
+
+- Added ``cles_khr_int64`` extension.
+
+- Added bug fixes and simplifications to Clang blocks in OpenCL mode.
+
+- Added compiler flag ``-cl-uniform-work-group-size`` to allow extra compile time optimisation.
+
+- Propagate ``denorms-are-zero`` attribute to IR if ``-cl-denorms-are-zero`` is passed to the compiler.
+
+- Separated ``read_only`` and ``write_only`` pipe IR types.
+
+- Fixed address space for the ``__func__`` predefined macro.
+
+- Improved diagnostics of kernel argument types.
+
+
+Started OpenCL C++ support:
+
+- Added ``-std/-cl-std=c++``.
+
+- Added support for keywords.
 
 OpenMP Support in Clang
 ----------------------------------