add so basic Mu docs

Author: moritz

lib/Mu.pod

@@ -0,0 +1,39 @@
+=begin pod
+
+=head1 Mu
+
+    class Mu { ... }
+
+The root of the Perl 6 type hierarchy. For the origin of the name, see
+L<http://en.wikipedia.org/wiki/Mu_%28negative%29>. One can also says that
+there are many undefined values in Perl 6, and C<Mu> is the I<most undefined>
+value.
+
+Note that most class do not derive from C<Mu> directly, but rather from
+L<Any>.
+
+=head2 Methods
+
+=head3 defined
+
+    multi sub    defined(Mu) returns Bool:D
+    multi method defined()   returns Bool:D
+
+Returns C<False> on the type object, and C<True> otherwise
+
+=head3 Bool
+
+    multi sub    Bool(Mu) returns Bool:D
+    multi method Bool()   returns Bool:D
+
+Returns C<False> on the type object, and C<True> otherwise
+
+=head3 clone
+
+    method clone(*%twiddles)
+
+Creates a shallow clone of the invocant. If named arguments are passed
+to it, their values are used in every place where an attribute name matches
+the name of a named argument.
+
+=end pod