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.

NEWS

@@ -12,6 +12,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 - Fixed a memory leak when restoring PATH when temporarily setting PATH
   for a command (e.g. PATH=/foo/bar command ...) or in a virtual subshell.
 
+- Combining ((...)) with redirections no longer causes a syntax error
+  due to the parser handling '>' incorrectly.
+
 2020-07-07:
 
 - Four of the date formats accepted by 'printf %()T' have had their