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/COMPATIBILITY

@@ -22,7 +22,10 @@ For more details, see the NEWS file and for complete details, see the git log.
 3.	The bash-style &>foo redirection operator (shorthand for >foo 2>&1) can
 	now always be used if -o posix is off, and not only in profile scripts.
 
-4.	Most predefined aliases have been converted to regular built-in
+4.	Redirections that store a file descriptor > 9 in a variable, such as
+	{var}>file, now continue to work if brace expansion is turned off.
+
+5.	Most predefined aliases have been converted to regular built-in
 	commands that work the same way. 'unalias' no longer removes these.
 	To remove a built-in command, use 'builtin -d'. The 'history' and 'r'
 	predefined aliases remain, but are now only set on interactive shells.
@@ -34,12 +37,12 @@ For more details, see the NEWS file and for complete details, see the git log.
 	   no parent shell to return to and the login session would freeze.
 	-  'times' now gives high precision output in a POSIX compliant format.
 
-5.	'command' no longer expands aliases in its first argument, as this is
-	no longer required after change 3 above. In the unlikely event that you
-	still need this behavior, you can set:
+6.	'command' no longer expands aliases in its first argument, as this is
+	no longer required after the foregoing change. In the unlikely event
+	that you still need this behavior, you can set:
 		alias command='command '
 
-6.	The undocumented 'login' and 'newgrp' builtin commands have been
+7.	The undocumented 'login' and 'newgrp' builtin commands have been
 	removed. These replaced your shell session with the external commands
 	by the same name, as in 'exec'. If an error occurred (e.g. due to a
 	typo), you would end up immediately logged out. If you do want this
@@ -47,7 +50,7 @@ For more details, see the NEWS file and for complete details, see the git log.
 		alias login='exec login'
 		alias newgrp='exec newgrp'
 
-7.	'case' no longer retries to match patterns as literal strings if they
+8.	'case' no longer retries to match patterns as literal strings if they
 	fail to match as patterns. This undocumented behaviour broke validation
 	use cases that are expected to work. For example:
 		n='[0-9]'
@@ -61,30 +64,30 @@ For more details, see the NEWS file and for complete details, see the git log.
 			echo "$n is a number or the number pattern" ;;
 		esac
 
-8.	If 'set -u'/'set -o nounset' is active, then the shell now errors out
+9.	If 'set -u'/'set -o nounset' is active, then the shell now errors out
 	if a nonexistent positional parameter such as $1, $2, ... is accessed.
 	(This does *not* apply to "$@" and "$*".)
 
-9.	If 'set -u'/'set -o nounset' is active, then the shell now errors out
+10.	If 'set -u'/'set -o nounset' is active, then the shell now errors out
 	if $! is accessed before the shell has launched any background process.
 
-10.	The 'print', 'printf' and 'echo' builtin commands now return a nonzero
+11.	The 'print', 'printf' and 'echo' builtin commands now return a nonzero
 	exit status if an input/output error occurs.
 
-11.	Four obsolete date format specifiers for 'printf %(format)T' were
+12.	Four obsolete date format specifiers for 'printf %(format)T' were
 	changed to make them compatible with modern date(1) commands:
 	- %k and %l now return a blank-padded hour (24-hour and 12-hour clock).
 	- %f now returns a date with the format '%Y.%m.%d-%H:%M:%S'.
 	- %q now returns the quarter of the current year.
 
-12.	The 'typeset' builtin now properly detects and reports options that
+13.	The 'typeset' builtin now properly detects and reports options that
 	cannot be used together if they are given as part of the same command.
 
-13.	The DEBUG trap has reverted to pre-93t behavior. It is now once again
+14.	The DEBUG trap has reverted to pre-93t behavior. It is now once again
 	reset like other traps upon entering a subshell or ksh-style function,
 	as documented, and it is no longer prone to crash or get corrupted.
 
-14.	'command -x' now always runs an external command, bypassing built-ins.
+15.	'command -x' now always runs an external command, bypassing built-ins.
 
 ____________________________________________________________________________