C++: Add deprecated to predicates that are deprecated according to the QLDoc

cpp/ql/lib/semmle/code/cpp/Declaration.qll

@@ -186,7 +186,7 @@ class Declaration extends Locatable, @declaration {
   predicate hasDefinition() { exists(this.getDefinition()) }
 
   /** DEPRECATED: Use `hasDefinition` instead. */
-  predicate isDefined() { this.hasDefinition() }
+  deprecated predicate isDefined() { this.hasDefinition() }
 
   /** Gets the preferred location of this declaration, if any. */
   override Location getLocation() { none() }

cpp/ql/lib/semmle/code/cpp/Function.qll

@@ -41,7 +41,7 @@ class Function extends Declaration, ControlFlowNode, AccessHolder, @function {
    * `min<int>(int, int) -> int`, and the full signature of the uninstantiated
    * template on the first line would be `min<T>(T, T) -> T`.
    */
-  string getFullSignature() {
+  deprecated string getFullSignature() {
     exists(string name, string templateArgs, string args |
       result = name + templateArgs + args + " -> " + this.getType().toString() and
       name = this.getQualifiedName() and

cpp/ql/lib/semmle/code/cpp/commons/Alloc.qll

@@ -12,7 +12,9 @@ predicate freeFunction(Function f, int argNum) { argNum = f.(DeallocationFunctio
  *
  * DEPRECATED: Use `DeallocationExpr` instead (this also includes `delete` expressions).
  */
-predicate freeCall(FunctionCall fc, Expr arg) { arg = fc.(DeallocationExpr).getFreedExpr() }
+deprecated predicate freeCall(FunctionCall fc, Expr arg) {
+  arg = fc.(DeallocationExpr).getFreedExpr()
+}
 
 /**
  * Is e some kind of allocation or deallocation (`new`, `alloc`, `realloc`, `delete`, `free` etc)?