Copy wxPerl notes from the LaTeX documentation.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62451 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/filesys.h

@@ -331,7 +331,7 @@ public:
 
     @beginWxPerlOnly
     In wxPerl, you need to derive your file system handler class
-    from Wx::PlFileSystemHandler.
+    from @c Wx::PlFileSystemHandler.
     @endWxPerlOnly
 
     @library{wxbase}