Import reduced tree patch

http://www.tt-forums.net/viewtopic.php?p=890778#p890778

Update to recent trunk, use extended savegame framework.
Add setting help text, tweak setting name.
Pre-calculate tree growth probabilities.

src/lang/english.txt

@@ -1663,6 +1663,13 @@ STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_HELPTEXT               :Adjust placemen
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_RANGE                  :Arctic tree range: {STRING2}
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_RANGE_HELPTEXT         :Approximate range of arctic trees around snow line
 
+STR_CONFIG_SETTING_TREE_GROWTH                                  :Tree growth speed: {STRING2}
+STR_CONFIG_SETTING_TREE_GROWTH_HELPTEXT                         :Control rate at which trees grow during the game. This might affect industries which rely on tree growth, for example lumber mills
+STR_CONFIG_SETTING_TREE_GROWTH_NORMAL                           :Normal
+STR_CONFIG_SETTING_TREE_GROWTH_SLOW                             :Slow
+STR_CONFIG_SETTING_TREE_GROWTH_VERY_SLOW                        :Very slow
+STR_CONFIG_SETTING_TREE_GROWTH_EXTREMLY_SLOW                    :Extremly slow
+
 STR_CONFIG_SETTING_TOOLBAR_POS                                  :Position of main toolbar: {STRING2}
 STR_CONFIG_SETTING_TOOLBAR_POS_HELPTEXT                         :Horizontal position of the main toolbar at the top of the screen
 STR_CONFIG_SETTING_STATUSBAR_POS                                :Position of status bar: {STRING2}

src/settings_gui.cpp

@@ -1788,6 +1788,7 @@ static SettingsContainer &GetSettingsTree()
 				treedist->Add(new SettingEntry("construction.extra_tree_placement"));
 				treedist->Add(new SettingEntry("construction.trees_around_snow_line_enabled"));
 				treedist->Add(new SettingEntry("construction.trees_around_snow_line_range"));
+				treedist->Add(new SettingEntry("construction.tree_growth_rate"));
 			}
 
 			environment->Add(new SettingEntry("station.modified_catchment"));

src/settings_type.h

@@ -359,6 +359,7 @@ struct ConstructionSettings {
 	uint16 clear_frame_burst;                ///< how many tiles may, over a short period, be cleared?
 	uint32 tree_per_64k_frames;              ///< how many trees may, over a long period, be planted per 65536 frames?
 	uint16 tree_frame_burst;                 ///< how many trees may, over a short period, be planted?
+	uint8  tree_growth_rate;                 ///< tree growth rate
 };
 
 /** Settings related to the AI. */

src/table/settings.ini

@@ -2744,6 +2744,20 @@ strval   = STR_JUST_COMMA
 cat      = SC_BASIC
 patxname = ""everest_treeline.construction.trees_around_snow_line_range""
 
+[SDT_VAR]
+base     = GameSettings
+var      = construction.tree_growth_rate
+type     = SLE_UINT8
+guiflags = SGF_MULTISTRING
+def      = 0
+min      = 0
+max      = 3
+str      = STR_CONFIG_SETTING_TREE_GROWTH
+strhelp  = STR_CONFIG_SETTING_TREE_GROWTH_HELPTEXT
+strval   = STR_CONFIG_SETTING_TREE_GROWTH_NORMAL
+cat      = SC_BASIC
+patxname = ""reduced_tree_growth.construction.tree_growth_rate""
+
 [SDT_VAR]
 base     = GameSettings
 var      = game_creation.custom_sea_level

src/tree_cmd.cpp

@@ -732,7 +732,16 @@ static void TileLoop_Trees(TileIndex tile)
 		}
 	}
 	if (GetTreeCounter(tile) < 15) {
-		AddTreeCounter(tile, 1);
+		if (_settings_game.construction.tree_growth_rate > 0) {
+			/* slow, very slow, extremely slow */
+			uint16 grow_slowing_values[3] = { 0x10000 / 5, 0x10000 / 20, 0x10000 / 120 };
+
+			if (GB(Random(), 0, 16) < grow_slowing_values[_settings_game.construction.tree_growth_rate - 1]) {
+				AddTreeCounter(tile, 1);
+			}
+		} else {
+			AddTreeCounter(tile, 1);
+		}
 		return;
 	}
 	SetTreeCounter(tile, 0);