tokenize: Add minimal stub to support linecache.

python-stdlib/tokenize/metadata.txt

@@ -0,0 +1,5 @@
+srctype = micropython-lib
+type = module
+version = 1.0
+author = Andrew Leech
+long_desc = Minimal tokenize stub supporting open() in utf8 encoding.

python-stdlib/tokenize/tokenize.py

@@ -0,0 +1,8 @@
+from builtins import open as _builtin_open
+
+
+def open(filename):
+    """Open a file in read only text mode using utf8.
+    """
+    return _builtin_open(filename, "r", encoding="utf8")
+