Procedurally draw combobox borders

This avoids issues with the borders looking bad when scaled

data/gui/default/widget/combobox_default.cfg

@@ -3,6 +3,19 @@
 ### Definition of the default button.
 ###
 
+#define _GUI_DRAW_BORDER
+	[rectangle]
+		x = 0
+		y = 0
+		w = "(width)"
+		h = "(height)"
+
+		border_thickness = 1
+		border_color = "114, 79, 46, 255"
+
+	[/rectangle]
+#enddef
+
 #define _GUI_RESOLUTION RESOLUTION MIN_WIDTH DEFAULT_WIDTH HEIGHT EXTRA_WIDTH EXTRA_HEIGHT FONT_SIZE BASE_NAME IPF
 	[resolution]
 
@@ -31,6 +44,8 @@
 					name = "buttons/{BASE_NAME}.png{IPF}"
 				[/image]
 
+				{_GUI_DRAW_BORDER}
+
 				{GUI__LEFT_TEXT ({FONT_SIZE}) () ({GUI__FONT_COLOR_ENABLED__TITLE})}
 
 				[image]
@@ -52,6 +67,8 @@
 					name = "buttons/{BASE_NAME}.png~GS(){IPF}"
 				[/image]
 
+				{_GUI_DRAW_BORDER}
+
 				{GUI__LEFT_TEXT ({FONT_SIZE}) () ({GUI__FONT_COLOR_DISABLED__TITLE})}
 
 				[image]
@@ -73,6 +90,8 @@
 					name = "buttons/{BASE_NAME}-pressed.png{IPF}"
 				[/image]
 
+				{_GUI_DRAW_BORDER}
+
 				{GUI__LEFT_TEXT ({FONT_SIZE}) () ({GUI__FONT_COLOR_ENABLED__TITLE})}
 
 				[image]
@@ -95,6 +114,8 @@
 					name = "buttons/{BASE_NAME}-pressed.png{IPF}"
 				[/image]
 
+				{_GUI_DRAW_BORDER}
+
 				{GUI__LEFT_TEXT ({FONT_SIZE}) () ({GUI__FONT_COLOR_ENABLED__TITLE})}
 
 				[image]
@@ -119,3 +140,4 @@
 [/combobox_definition]
 
 #undef _GUI_RESOLUTION
+#undef _GUI_DRAW_BORDER