gui2/preferences: Add version info button

Also simplifies the layout of the bottom-most row of the dialog a bit.

changelog.md

@@ -24,6 +24,7 @@
    * Fixed the first unit sometimes not being selected when opening the Recall
      dialog.
    * Fixed a crash when using very large portraits in [message] (issue #2912)
+   * Added a button to access the version info dialog to Preferences.
  ### Terrains
    * Removed hidden terrains that were not supposed to make it to 1.14: ^Prg,
      ^Prgo, ^Pwd, ^Pwdo

data/gui/window/preferences.cfg

@@ -408,33 +408,24 @@
 
 			[row]
 
-				{GUI_FILLER}
+				[column]
+					horizontal_alignment = "left"
+					[button]
+						id = "about"
+						definition = "action_about"
+						tooltip = _ "Display the game version and build information"
+					[/button]
+				[/column]
 
 				[column]
 					horizontal_alignment = "right"
-
-					[grid]
-
-						[row]
-							grow_factor = 0
-
-							{GUI_FILLER}
-
-							[column]
-								border = "all"
-								border_size = 5
-								horizontal_alignment = "right"
-								[button]
-									id = "ok"
-									definition = "default"
-									label = _ "Close"
-								[/button]
-							[/column]
-
-						[/row]
-
-					[/grid]
-
+					border = "all"
+					border_size = 5
+					[button]
+						id = "ok"
+						definition = "default"
+						label = _ "Close"
+					[/button]
 				[/column]
 
 			[/row]

src/gui/dialogs/preferences_dialog.cpp

@@ -40,6 +40,7 @@
 #include "gui/dialogs/select_orb_colors.hpp"
 
 #include "gui/auxiliary/find_widget.hpp"
+#include "gui/dialogs/game_version.hpp"
 #include "gui/dialogs/message.hpp"
 #include "gui/dialogs/transient_message.hpp"
 #include "gui/widgets/button.hpp"
@@ -997,6 +998,8 @@ void preferences_dialog::pre_show(window& window)
 {
 	set_always_save_fields(true);
 
+	connect_signal_mouse_left_click(find_widget<button>(&window, "about", false), std::bind(&game_version::display<>));
+
 	//
 	// Status labels
 	// These need to be set here in pre_show, once the fields are initialized. For some reason, this