Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/@python2/mimetools.pyi

@@ -0,0 +1,27 @@
+import rfc822
+from typing import Any
+
+class Message(rfc822.Message):
+    encodingheader: Any
+    typeheader: Any
+    def __init__(self, fp, seekable: int = ...): ...
+    plisttext: Any
+    type: Any
+    maintype: Any
+    subtype: Any
+    def parsetype(self): ...
+    plist: Any
+    def parseplist(self): ...
+    def getplist(self): ...
+    def getparam(self, name): ...
+    def getparamnames(self): ...
+    def getencoding(self): ...
+    def gettype(self): ...
+    def getmaintype(self): ...
+    def getsubtype(self): ...
+
+def choose_boundary(): ...
+def decode(input, output, encoding): ...
+def encode(input, output, encoding): ...
+def copyliteral(input, output): ...
+def copybinary(input, output): ...