Added a note about compiler warnings.

Mac/Demo/building.html

@@ -332,6 +332,10 @@ and setting the filetype to APPL (with ResEdit or some such). <p>
 Fullbuild does this for you, and the Atmp files is also how ConfigurePythonCarbon
 and ConfigurePythonClassic work their magic. <p>
 
+You will get about 100 warnings on "missing prototype" for the various module init
+routines, ignore these. You will also get numerous warnings on functions from GUSI which
+override functions from MSL, ignore these too. <p>
+
 For completeness sake here is a breakdown of the projects:
 
 <DL>