[Feature]String Literal Hash Optimization

YoYoGames/GameMaker-Bugs#2804
YoYoGames/GameMaker-Bugs#2821
* Added a note under "Struct Functions" on the Variable Functions page

Manual/contents/GameMaker_Language/GML_Reference/Variable_Functions/Variable_Functions.htm

@@ -42,6 +42,7 @@ <h2 id="method_functions">Method Functions</h2>
     <li><a data-xref="{title}" href="method_call.htm">method_call</a></li>
   </ul>
   <h2 id="struct_functions">Struct Functions</h2>
+  <p class="note"><span data-conref="../../../assets/snippets/Tag_note.hts"> </span> As an optimisation, the compiler replaces struct member names in these functions with their hash value when it detects that the name is a constant at compile-time.</p>
   <p>The following functions are for use with structs:</p>
   <ul class="colour">
     <li><a data-xref="{title}" href="variable_struct_exists.htm">struct_exists</a></li>