ash: fix error code regression

The commit 'ash,hush: set exit code 127 in "sh /does/not/exist" case'
only partly implemented the dash commit '[ERROR] Allow the originator
of EXERROR to set the exit status'.  This resulted in incorrect error
codes for a syntax error:

   $ )
   $ echo $?
   0

or a redirection error for a special builtin:

   $ rm -f xxx
   $ eval cat <xxx
   $ echo $?
   0

Signed-off-by: Ron Yorston <rmy@pobox.com>
Reported-by: Martijn Dekker <martijn@inlv.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-misc/exitcode2.tests

@@ -0,0 +1,12 @@
+# syntax error should return status 2
+cat >test.sh <<EOF
+)
+EOF
+chmod +x test.sh
+$THIS_SH ./test.sh
+echo Done:$?
+rm -f test.sh
+
+# redirection error with special builtin should return status 1
+(eval cat <does_not_exist)
+echo Done:$?