hush: fix heredoc expansion of $var and cmd

function                                             old     new   delta
expand_pseudo_dquoted                                  -     104    +104
setup_heredoc                                        215     275     +60
done_word                                            669     691     +22
parse_stream                                        1899    1902      +3
setup_redirects                                      196     191      -5
free_pipe                                            189     183      -6
expand_variables                                    2349    2229    -120
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/3 up/down: 189/-131)           Total: 58 bytes

shell/hush_test/hush-misc/heredoc2.right

@@ -1,6 +1,7 @@
 exit EOF-f
 "
 echo 1
+echo Hello World
 moo	 
  EOF-f
 EOF-f   f

shell/hush_test/hush-misc/heredoc2.tests

@@ -3,6 +3,7 @@ f=1
 		exit EOF-f
 "
 echo $f
+echo `echo Hello World`
 		moo	 
  EOF-f
 EOF-f   f

shell/hush_test/hush-misc/heredoc3.right

@@ -0,0 +1,8 @@
+exit EOF-f
+"
+echo $f
+echo `echo Hello World`
+moo	 
+ EOF-f
+EOF-f   f
+EOF-f 

shell/hush_test/hush-misc/heredoc3.tests

@@ -0,0 +1,11 @@
+f=1
+  cat <<- EOF-f""
+		exit EOF-f
+"
+echo $f
+echo `echo Hello World`
+		moo	 
+ EOF-f
+EOF-f   f
+EOF-f 
+EOF-f