Make redirections like {varname}>file work with brace expansion off

This is some nonsense: redirections that store a file descriptor
greater than 9 in a variable, like {var}<&2 and the like, stopped
working if brace expansion was turned off. '{var}' is not a brace
expansion as it doesn't contain ',' or '..'; something like 'echo
{var}' is always output unexpanded. And redirections and brace
expansion are two completely unrelated things. It wasn't documented
that these redirections require the -B/braceexpand option, either.

src/cmd/ksh93/sh/lex.c: sh_lex():
- Remove incorrect check for braceexpand option before processing
  redirections of this form.

src/cmd/ksh93/COMPATIBILITY:
- Insert a brief item mentioning this.

src/cmd/ksh93/sh.1:
- Correction: these redirections do not yield a file descriptor >
  10, but > 9, a.k.a. >= 10.
- Add a brief example showing how these redirections can be used.

src/cmd/ksh93/tests/io.sh:
- Add a quick regression test.

src/cmd/ksh93/sh/lex.c

@@ -1347,10 +1347,11 @@ breakloop:
 			c = (wordflags&ARG_EXP);
 		n = 1;
 	}
-	else if(n>2 && state[0]=='{' && state[n-1]=='}' && !lp->lex.intest && !lp->lex.incase && (c=='<' || c== '>') && sh_isoption(SH_BRACEEXPAND))
+	else if(n>2 && state[0]=='{' && state[n-1]=='}' && !lp->lex.intest && !lp->lex.incase && (c=='<' || c== '>'))
 	{
 		if(!strchr(state,','))
 		{
+			/* Redirection of the form {varname}>file, etc. */
 			stkseek(stkp,stktell(stkp)-1);
 			lp->arg = (struct argnod*)stkfreeze(stkp,1);
 			return(lp->token=IOVNAME);