Update codeql custom query

admin/codeql/custom-queries/cpp/codeql-pack.yml

@@ -0,0 +1,4 @@
+name: ultrascan3-cpp-queries
+version: 0.0.1
+dependencies:
+  codeql/cpp-all: "*"

admin/codeql/custom-queries/cpp/find-unused-functions.ql

@@ -1,13 +1,14 @@
 /**
  * @name Unused function
- * @description Finds unused functions in C/C++ code.
+ * @description Finds functions in the codebase that are defined but never called.
  * @kind problem
  * @problem.severity warning
+ * @id cpp/unused-function
+ * @tags performance, maintainability
  */
 import cpp
 
 from Function func
-where not func.isExtern() and
-      not func.isEntryPoint() and
-      func.getNumberOfCallers() = 0
+where exists(Location loc | func.getLocation() = loc) and
+      not exists(Call call | call.getTarget() = func)
 select func, "This function is never used."