Fix 'redirect {var}>file' in subshell (re: 7b82c338)

Permanent redirections of that form broke in subshells when used
with the 'redirect' command, because I had overlooked one instance
where the new 'redirect' builtin needs to match the behaviour of
the 'exec' builtin.

src/cmd/ksh93/tests/io.sh: sh_exec():
- Do not restore file descriptors in (virtual) subshells for
  'redirect' just as this isn't done for 'exec'.

src/cmd/ksh93/tests/io.sh:
- Add regression test for this bug.
- Complete the test for f9427909 which I committed prematurely.

Fixes: https://github.com/ksh93/ksh/issues/167

src/cmd/ksh93/sh/xec.c

@@ -1401,8 +1401,8 @@ int sh_exec(register const Shnode_t *t, int flags)
 						sh_unscope(shp);
 					bp->ptr = (void*)save_ptr;
 					bp->data = (void*)save_data;
-					/* don't restore for subshell exec */
-					if((shp->topfd>topfd) && !(shp->subshell && np==SYSEXEC))
+					/* don't restore for 'exec' or 'redirect' in subshell */
+					if((shp->topfd>topfd) && !(shp->subshell && (np==SYSEXEC || np==SYSREDIR)))
 						sh_iorestore(shp,topfd,jmpval);
 			
 					shp->redir0 = 0;

src/cmd/ksh93/tests/io.sh

@@ -698,8 +698,13 @@ got=$(export tmp; "$SHELL" -ec \
 
 # ======
 # Redirections of the form {varname}>file stopped working if brace expansion was turned off
-redirect {v}>$tmp/v.out; echo ok >&$v
-[[ $(<$tmp/v.out) == ok ]] || err_exit '{varname}>file not working with brace expansion turned off'
+set +B
+{ redirect {v}>$tmp/v.out && echo ok >&$v; } 2>/dev/null
+set -B
+[[ -r $tmp/v.out && $(<$tmp/v.out) == ok ]] || err_exit '{varname}>file not working with brace expansion turned off'
+# ...and they didn't work in subshells: https://github.com/ksh93/ksh/issues/167
+(redirect {v}>$tmp/v.out; echo ok2 >&$v) 2>/dev/null
+[[ -r $tmp/v.out && $(<$tmp/v.out) == ok2 ]] || err_exit 'redirect {varname}>file not working in a subshell'
 
 # ======
 exit $((Errors<125?Errors:125))