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/tests/arith.sh

@@ -761,4 +761,9 @@ x=0x1.0000000000000000000000000000p+6
 v=$(printf $'%.28a\n' 64)
 [[ $v == "$x" ]] || err_exit "'printf %.28a 64' failed -- expected '$x', got '$v'"
 
+# ======
+# Redirections with ((...)) should not cause a syntax error
+(eval '((1)) >/dev/null') 2>/dev/null || err_exit 'redirections with ((...)) yield a syntax error'
+
+# ======
 exit $((Errors<125?Errors:125))