Exclude members of uninstantiated templates

We can't properly determine the use of uninstantiated template members
without looking at all the instantiated templates.
Even then, included templates provide an interface that can be partially
used, so alerting on those parts that are currently not used doesn't
necessarily indicate a programming mistake.

Author: rvermeulen

cpp/common/src/codingstandards/cpp/deadcode/UnusedVariables.qll

@@ -92,7 +92,9 @@ class PotentiallyUnusedMemberVariable extends MemberVariable {
     // Must be in a fully defined class, otherwise one of the undefined functions may use the variable
     getDeclaringType() instanceof FullyDefinedClass and
     // Lambda captures are not "real" member variables - it's an implementation detail that they are represented that way
-    not this = any(LambdaCapture lc).getField()
+    not this = any(LambdaCapture lc).getField() and
+    // exclude uninstantiated template members
+    not this.isFromUninstantiatedTemplate(_)
   }
 }