Fix a syntax error when ((...)) is combined with redirections (#68)

This bugfix was backported from ksh93v- 2013-10-10-alpha.

src/cmd/ksh93/sh/parse: item():
- The done label is placed after the 'inout' call for handling I/O
  redirections. This causes the command below to produce a syntax
  error because the '>' is not handled as a redirection operator
  after 'goto done':
  $ ((1+2)) > /dev/null
  /usr/bin/ksh: syntax error: `>' unexpected
  Moving the done label fixes the syntax error as 'inout' is now
  called to handle the redirection operator.

src/cmd/ksh93/tests/arith.sh:
- Add a simple regression test.

src/cmd/ksh93/sh/parse.c

@@ -1367,13 +1367,13 @@ static Shnode_t	*item(Lex_t *lexp,int flag)
 		return(t);
 	}
 	sh_lex(lexp);
-	/* redirection(s) following a compound command */
+done:
+	/* redirection(s) following a compound command or arithmetic expression */
 	if(io=inout(lexp,io,0))
 	{
 		t=makeparent(lexp,TSETIO,t);
 		t->tre.treio=io;
 	}
-done:
 	lexp->lasttok = savwdval;
 	lexp->lastline = savline;
 	return(t);