Update changelog for 11.2 release (#7165)

Creates a new changelog section for post-11.2 changes.

api/docs/release.dox

@@ -124,7 +124,17 @@ Dr. Memory Framework (DRMF) in the same package as DynamoRIO.  DRMF
 provides the umbra, drsyscall, and drsymcache Extensions for use by
 clients.
 
-The changes between version \DR_VERSION and 11.1.0 include the following compatibility
+The changes between version \DR_VERSION and 11.2.0 include the following compatibility
+changes:
+ - No compatibility changes yet.
+
+Further non-compatibility-affecting changes include:
+ - No changes yet.
+
+**************************************************
+<hr>
+
+The changes between version 11.2.0 and 11.1.0 include the following compatibility
 changes:
  - Added #dynamorio::drmemtrace::TRACE_ENTRY_VERSION_RETIRED_INSTRUCTIONS_ONLY to increase the
    trace version for drmemtraces with uncompleted instructions removed.