ReleaseNotes: -fstrict-vtable-pointers, by Piotr Padlewski

git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_38@262523 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ReleaseNotes.rst

@@ -70,6 +70,9 @@ debugger. Clang supports tuning for three debuggers, as follows.
 
 Specifying ``-g`` without a tuning option will use a target-dependent default.
 
+The new ``-fstrict-vtable-pointers`` flag enables better devirtualization
+support (experimental).
+
 
 New Pragmas in Clang
 -----------------------