Implement dict() style constructor.
Already supported dict() and dict(mapping).
Now supports dict(itemsequence) and
Just van Rossum's new syntax for dict(keywordargs).

Also, added related unittests.

The docs already promise dict-like behavior
so no update is needed there.
diff --git a/Lib/test/test_userdict.py b/Lib/test/test_userdict.py
index a59419d..b561ac1 100644
--- a/Lib/test/test_userdict.py
+++ b/Lib/test/test_userdict.py
@@ -19,6 +19,9 @@
 uu1 = UserDict(u1)
 uu2 = UserDict(u2)
 
+verify(UserDict(one=1, two=2) == d2)            # keyword arg constructor
+verify(UserDict([('one',1), ('two',2)]) == d2)  # item sequence constructor
+
 # Test __repr__
 
 verify(str(u0) == str(d0))