(svn r12022) -Revert(r12018): Invisible trees are now separate from the building concept.

So when you want invisible trees, just select the option of the same name in the Patch Options and toggle transparency of trees.
More to come on the saga of Invisibility. So stay tuned.

src/transparency_gui.cpp

@@ -7,7 +7,6 @@
 #include "variables.h"
 #include "transparency.h"
 #include "sound_func.h"
-#include "settings_type.h"
 
 #include "table/sprites.h"
 #include "table/strings.h"
@@ -39,10 +38,6 @@ static void TransparencyToolbWndProc(Window *w, WindowEvent *e)
 				w->SetWidgetLoweredState(i, IsTransparencySet((TransparencyOption)(i - TTW_WIDGET_SIGNS)));
 			}
 
-			/* Disabling the trees button allows to make it very evident that it has no effect
-			 * upon current situation */
-			w->SetWidgetDisabledState(TTW_WIDGET_TREES, _patches.invisible_trees && IsTransparencySet(TO_HOUSES));
-
 			DrawWindowWidgets(w);
 			break;