Revert "Remove mod name from tooltips"

This reverts commit 64b0248c772966766c0bd3d6f0f47b96ff60625c.

The mod name may differ from the item name, in which cases it is
helpful to have this information contained in the tooltip.
No information is shown in case the mod name is missing.

internal.lua

@@ -256,8 +256,14 @@ local function formspec_add_item_browser(player, formspec, ui_peruser)
 					ui_peruser.btn_size, ui_peruser.btn_size,
 					name, button_name
 				)
+				local tooltip = item.description
+				if item.mod_origin then
+					-- "mod_origin" may not be specified for items that were
+					-- registered in a callback (during or before ServerEnv init)
+					tooltip = tooltip .. " [" .. item.mod_origin .. "]"
+				end
 				formspec[n + 1] = ("tooltip[%s;%s]"):format(
-					button_name, minetest.formspec_escape(item.description)
+					button_name, minetest.formspec_escape(tooltip)
 				)
 				n = n + 2
 				list_index = list_index + 1