C++: respond to PR comments

cpp/ql/src/Likely Bugs/Likely Typos/FutileParams.qhelp

@@ -8,6 +8,11 @@
 <p>A function is called with arguments despite having an empty parameter list. This may indicate
 that the incorrect function is being called, or that the author misunderstood the function.</p>
 
+<p>In C, a function declared with an empty parameter list `()` is considered to have an unknown
+parameter list, and therefore can be called with any set of arguments. To declare a function
+which takes no arguments, you must use `(void)` as the parameter list in any forward declarations.
+In C++, either style of declaration will be considered to take no arguments.</p>
+
 </overview>
 <recommendation>
 <p>Call the function without arguments, or call a different function that expects the arguments

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/FutileParams/test.c

@@ -14,12 +14,12 @@ void test() {
   not_yet_declared1(1); // BAD
   not_yet_declared2(1); // GOOD
 
-  declared_empty_defined_with(); // BAD
+  declared_empty_defined_with(); // BAD [NOT DETECTED]
   declared_empty_defined_with(1); // GOOD
 
   int x;
-  declared_empty_defined_with(&x); // BAD
-  declared_empty_defined_with(x, x); // BAD
+  declared_empty_defined_with(&x); // BAD [NOT DETECTED]
+  declared_empty_defined_with(x, x); // BAD [NOT DETECTED]
 }
 
 void not_yet_declared1();