Add rand as a term, cloning the Nil term's code.

Apparently this still needs special handling to get properly awesome error messages, but for the moment, this works.

src/Perl6/Actions.pm

@@ -1380,6 +1380,10 @@ method term:sym<Nil>($/) {
     make PAST::Op.new(:name('&Nil'), :node($/) );
 }
 
+method term:sym<rand>($/) {
+    make PAST::Op.new(:name('&rand'), :node($/) );
+}
+
 method term:sym<...>($/) {
     make PAST::Op.new( :pasttype('call'), :name('&fail'), 'Stub code executed', :node($/) );
 }

src/Perl6/Grammar.pm

@@ -775,7 +775,8 @@ proto token term { <...> }
 
 token term:sym<self> { <sym> <.nofun> }
 
-token term:sym<Nil> { <sym> <.nofun> }
+token term:sym<Nil>  { <sym> <.nofun> }
+token term:sym<rand> { <sym> <.nofun> }
 
 token term:sym<...> { <sym> <args>? }
 token term:sym<???> { <sym> <args>? }