add test case for name normalization in tail call optimization

Author: jvoigtlaender

tests/test-files/good-expected-js/CodeGenBugs/TailRecursion_NameNormalization.elm.js

@@ -0,0 +1,10 @@
+Elm.Main = Elm.Main || {};
+Elm.Main.make = function (_elm) {
+   "use strict";
+   _elm.Main = _elm.Main || {};
+   if (_elm.Main.values) return _elm.Main.values;
+   var _U = Elm.Native.Utils.make(_elm);
+   var _op = {};
+   var go = function (n$) {    go: while (true) if (n$) {    var _v0 = n$;n$ = _v0;continue go;} else return false;};
+   return _elm.Main.values = {_op: _op,go: go};
+};

tests/test-files/good/CodeGenBugs/TailRecursion_NameNormalization.elm

@@ -0,0 +1,8 @@
+-- From https://github.com/elm-lang/elm-compiler/issues/1226
+--
+-- When code can be tail call optimized, one of the arguments turns into
+-- the loop variable. Its name must be properly normalized, for example,
+-- to avoid primes.
+
+go n' = if n' then go n' else False
+