Dump doesn't need to reuse 'source'

All strings are being reused now, including 'source'.

testes/calls.lua

@@ -487,5 +487,30 @@ do
   end
 end
 
+
+do   -- check reuse of strings in dumps
+  local str = "|" .. string.rep("X", 50) .. "|"
+  local foo = load(string.format([[
+    local str <const> = "%s"
+    return {
+      function () return str end,
+      function () return str end,
+      function () return str end
+    }
+  ]], str))
+  -- count occurrences of 'str' inside the dump
+  local dump = string.dump(foo)
+  local _, count = string.gsub(dump, str, {})
+  -- there should be only two occurrences:
+  -- one inside the source, other the string itself.
+  assert(count == 2)
+
+  if T then  -- check reuse of strings in undump
+    local funcs = load(dump)()
+    assert(string.format("%p", T.listk(funcs[1])[1]) ==
+           string.format("%p", T.listk(funcs[3])[1]))
+  end
+end
+
 print('OK')
 return deep