C++: Add a 1.26 change note file (what happened to the templates?)

Author: geoffw0

change-notes/1.26/analysis-cpp.md

@@ -0,0 +1,18 @@
+# Improvements to C/C++ analysis
+
+The following changes in version 1.26 affect C/C++ analysis in all applications.
+
+## General improvements
+
+## New queries
+
+| **Query**                   | **Tags**  | **Purpose**                                                        |
+|-----------------------------|-----------|--------------------------------------------------------------------|
+
+## Changes to existing queries
+
+| **Query**                  | **Expected impact**    | **Change**                                                       |
+|----------------------------|------------------------|------------------------------------------------------------------|
+
+## Changes to libraries
+