Rearrange the setting of project snap-to...

... Just one low-level function to simply set the variable, and one
high-level function that also pushes notifications.  The danger of infinite
recursion in the toolbar code, as in the previous commit, doesn't exist here.

src/menus/HelpMenus.cpp

@@ -250,7 +250,7 @@ void QuickFixDialog::OnFix(wxCommandEvent &event)
       // preference dialogs.
       if( Str == "/SnapTo" )
       {
-         pProject->SetSnapTo( 0 );
+         pProject->AS_SetSnapTo( 0 );
       }
       else
       {