C++: Improve qhelp for IncorrectNotOperatorUsage.ql, including mention of an alternative fix.

Author: geoffw0

cpp/ql/src/Likely Bugs/Likely Typos/IncorrectNotOperatorUsage.cpp

@@ -2,7 +2,7 @@
 
 void f_warning(int i)
 {
-    // The usage of the logical not operator in this case is unlikely to be correct
+    // BAD: the usage of the logical not operator in this case is unlikely to be correct
     // as the output is being used as an operator for a bit-wise and operation
     if (i & !FLAGS)
     {
@@ -12,7 +12,7 @@ void f_warning(int i)
 
 void f_fixed(int i)
 {
-    if (i & ~FLAGS) // Changing the logical not operator for the bit-wise not operator would fix this logic
+    if (i & ~FLAGS) // GOOD: Changing the logical not operator for the bit-wise not operator would fix this logic
     {
         // code
     }

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

@@ -16,7 +16,9 @@
 <p>Carefully inspect the flagged expressions. Consider the intent in the code logic, and decide whether it is necessary to change the not operator.</p>
 </recommendation>
 
+<p>Here is an example of this issue and how it can be fixed:</p>
 <example><sample src="IncorrectNotOperatorUsage.cpp" /></example>
+<p>In other cases, particularly when the expressions have <code>bool</code> type, the fix may instead be of the form <code>a &amp;&amp; !b</code></p>
 
 <references>
   <li>