* Migrate set() and frozenset() from the sandbox.

* Install the unittests, docs, newsitem, include file, and makefile update.
* Exercise the new functions whereever sets.py was being used.

Includes the docs for libfuncs.tex.  Separate docs for the types are
forthcoming.

Doc/lib/libfuncs.tex

@@ -477,6 +477,17 @@ class C:
   and is known to vary.}
 \end{funcdesc}
 
+\begin{funcdesc}{frozenset}{\optional{iterable}}
+  Return a frozenset object whose elements are taken from \var{iterable}.
+  Frozensets are sets that have no update methods but can be hashed and
+  used as members of other sets or as dictionary keys.  The elements of
+  a frozenset must be immutable themselves.  To represent sets of sets,
+  the inner sets should also be \class{frozenset} objects.  If
+  \var{iterable} is not specified, returns a new empty set,
+  \code{frozenset([])}.
+  \versionadded{2.4}  
+\end{funcdesc}
+
 \begin{funcdesc}{getattr}{object, name\optional{, default}}
   Return the value of the named attributed of \var{object}.  \var{name}
   must be a string.  If the string is the name of one of the object's
@@ -897,6 +908,14 @@ class C(object):
   \code{round(0.5)} is \code{1.0} and \code{round(-0.5)} is \code{-1.0}).
 \end{funcdesc}
 
+\begin{funcdesc}{set}{\optional{iterable}}
+  Return a set whose elements are taken from \var{iterable}.  The elements
+  must be immutable.  To represent sets of sets, the inner sets should
+  be \class{frozenset} objects.  If \var{iterable} is not specified,
+  returns a new empty set, \code{set([])}.
+  \versionadded{2.4}  
+\end{funcdesc}
+
 \begin{funcdesc}{setattr}{object, name, value}
   This is the counterpart of \function{getattr()}.  The arguments are an
   object, a string and an arbitrary value.  The string may name an