C++: Promote cpp/guarded-free

Author: jketema

cpp/ql/src/experimental/Best Practices/GuardedFree.cpp renamed to cpp/ql/src/Best Practices/GuardedFree.cpp

@@ -1,18 +1,28 @@
-<!DOCTYPE qhelp SYSTEM "qhelp.dtd">
-<qhelp>
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp><qhelp>
+
 <overview>
 <p>The <code>free</code> function, which deallocates heap memory, may accept a NULL pointer and take no action. Therefore, it is unnecessary to check its argument for the value of NULL before a function call to <code>free</code>. As such, these guards may hinder performance and readability.</p>
 </overview>
+
 <recommendation>
-<p>A function call to <code>free</code> should not depend upon the value of its argument. Delete the <code>if</code> condition preceeding a function call to <code>free</code> when its only purpose is to check the value of the pointer to be freed.</p>
+<p>A function call to <code>free</code> should not depend upon the value of its argument. Delete the condition preceding a function call to <code>free</code> when its only purpose is to check the value of the pointer to be freed.</p>
 </recommendation>
+
 <example>
 <sample src = "GuardedFree.cpp" />
+
+<p>In this example the condition checking the value of <code>foo</code> can be deleted.
+
 </example>
+
 <references>
 <li>
     The Open Group Base Specifications Issue 7, 2018 Edition:
     <a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/free.html">free - free allocated memory</a>
 </li>
 </references>
-</qhelp>
+
+</qhelp>

cpp/ql/src/experimental/Best Practices/GuardedFree.qhelp renamed to cpp/ql/src/Best Practices/GuardedFree.qhelp

@@ -8,7 +8,6 @@
  * @id cpp/guarded-free
  * @tags maintainability
  *       readability
- *       experimental
  */
 
 import cpp