Apply diff3.txt (plus additional documentation)
from SF patch http://www.python.org/sf/554192

This adds two new functions to mimetypes:
guess_all_extensions() which returns a list of all known
extensions for a mime type, and add_type() which adds one
mapping between a mime type and an extension.
diff --git a/Misc/NEWS b/Misc/NEWS
index b877703..d08bc34 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -321,6 +321,11 @@
 
 Library
 
+- mimetypes has two new functions: guess_all_extensions() which
+  returns a list of all known extensions for a mime type, and
+  add_type() which adds one mapping between a mime type and
+  an extension to the database.
+
 - New module: sets, defines the class Set that implements a mutable
   set type using the keys of a dict to represent the set.  There's
   also a class ImmutableSet which is useful when you need sets of sets