cpp: Adds a member predicate to get a FunctionAccess from a Function

- Adds a member predicate to get a FunctionAccess from a Function
- Adds QLDoc to getACallToThisFunction.

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

@@ -139,6 +139,13 @@ class Function extends Declaration, ControlFlowNode, AccessHolder, @function {
   /** Gets a parameter of this function. */
   Parameter getAParameter() { params(unresolveElement(result), underlyingElement(this), _, _) }
 
+  /**
+   * Gets an access of this function.
+   *
+   * To get calls to this function, use `getACallToThisFunction` instead.
+   */
+  FunctionAccess getAnAccess() { result.getTarget() = this }
+
   /**
    * Gets the number of parameters of this function, _not_ including any
    * implicit `this` parameter or any `...` varargs pseudo-parameter.
@@ -174,6 +181,7 @@ class Function extends Declaration, ControlFlowNode, AccessHolder, @function {
     result = getParameter(index).getTypedName() + ", " + getParameterStringFrom(index + 1)
   }
 
+  /** Gets a call to this function. */
   FunctionCall getACallToThisFunction() { result.getTarget() = this }
 
   /**