Fixes Lua script line numbers in json_test

The error messages are line-number specific and they have shifted after
rebasing off of layeh/gopher-json master.

json_test.go

@@ -46,13 +46,13 @@ func TestSimple(t *testing.T) {
 	assert(json.decode("null") == nil)
 
 	local status, err = pcall(function() json.decode() end)
-	assert(err == "<string>:35: bad argument #1 to decode", err)
+	assert(err == "<string>:38: bad argument #1 to decode", err)
 	local status, err = pcall(function() json.decode(1,2) end)
-	assert(err == "<string>:37: bad argument #1 to decode", err)
+	assert(err == "<string>:40: bad argument #1 to decode", err)
 	local status, err = pcall(function() json.encode() end)
-	assert(err == "<string>:39: bad argument #1 to encode", err)
+	assert(err == "<string>:42: bad argument #1 to encode", err)
 	local status, err = pcall(function() json.encode(1,2) end)
-	assert(err == "<string>:41: bad argument #1 to encode", err)
+	assert(err == "<string>:44: bad argument #1 to encode", err)
 
 	assert(json.decode(json.encode({person={name = "tim",}})).person.name == "tim")