Complete a merge of the mimelib project and the Python cvs codebases

for the email package.  The former is now just a shell project that
has some extra files for packaging for independent use (e.g. setup.py
and README).

Added a compatibility layer so that the same API can be used in Python
2.1 and 2.2/2.3 with the major differences shuffled off into helper
modules (_compat21.py and _compat22.py).

Also bumped the package version number to 2.0.3 for some fixes to be
checked in momentarily.

Lib/email/_compat22.py

@@ -0,0 +1,56 @@
+# Copyright (C) 2002 Python Software Foundation
+# Author: barry@zope.com
+
+"""Module containing compatibility functions for Python 2.1.
+"""
+
+from __future__ import generators
+from __future__ import division
+from cStringIO import StringIO
+from types import StringTypes
+
+
+
+# This function will become a method of the Message class
+def walk(self):
+    """Walk over the message tree, yielding each subpart.
+
+    The walk is performed in depth-first order.  This method is a
+    generator.
+    """
+    yield self
+    if self.is_multipart():
+        for subpart in self.get_payload():
+            for subsubpart in subpart.walk():
+                yield subsubpart
+
+
+# Used internally by the Header class
+def _intdiv2(i):
+    """Do an integer divide by 2."""
+    return i // 2
+
+
+
+# These two functions are imported into the Iterators.py interface module.
+# The Python 2.2 version uses generators for efficiency.
+def body_line_iterator(msg):
+    """Iterate over the parts, returning string payloads line-by-line."""
+    for subpart in msg.walk():
+        payload = subpart.get_payload()
+        if isinstance(payload, StringTypes):
+            for line in StringIO(payload):
+                yield line
+
+
+def typed_subpart_iterator(msg, maintype='text', subtype=None):
+    """Iterate over the subparts with a given MIME type.
+
+    Use `maintype' as the main MIME type to match against; this defaults to
+    "text".  Optional `subtype' is the MIME subtype to match against; if
+    omitted, only the main type is matched.
+    """
+    for subpart in msg.walk():
+        if subpart.get_main_type('text') == maintype:
+            if subtype is None or subpart.get_subtype('plain') == subtype:
+                yield subpart