Multiple changes to DisplayServerX11

- Travis: Change x11 to linuxbsd
- SCons: Change x11 plataform to linuxbsd
- Plugins: Remove ; to avoid fallthrough warning
- DisplayServerX11: Implement set_icon
- DisplayServerX11: Fix X11 bug when a window was erased from windows
  map, all the changes from that erased windows are sending to the main
  window
- DisplayServerX11: Reorder create_window commands
- DisplayServerX11: Change every Size2 to Size2i and Rect2 to Rect2i
  where it belongs

+ More X11 fixes which have been integrated directly back into reduz's
original commits while rebasing the branch.

scene/gui/text_edit.cpp

@@ -5062,7 +5062,7 @@ void TextEdit::_update_caches() {
 #ifdef TOOLS_ENABLED
 	cache.line_spacing = get_theme_constant("line_spacing") * EDSCALE;
 #else
-	cache.line_spacing = get_constant("line_spacing");
+	cache.line_spacing = get_theme_constant("line_spacing");
 #endif
 	cache.row_height = cache.font->get_height() + cache.line_spacing;
 	cache.tab_icon = get_theme_icon("tab");