Fix how unrecognized options are handled in 'sleep' and 'suspend' (#93)

When a builtin is given an unrecognized option, the usage information
for that builtin should be shown as 'Usage: builtin-name options'. The
sleep and suspend builtins were an exception to this. 'suspend' would
not show usage information and sleep wouldn't exit on error:

$ suspend -e
/usr/bin/ksh: suspend: -e: unknown option
$ time sleep -e 1
sleep: -e: unknown option

real	0m1.00s
user	0m0.00s
sys	0m0.00s

src/cmd/ksh93/bltins/sleep.c:
- Show usage information and exit when sleep is given an unknown
  option. This bugfix was backported from ksh2020: https://github.com/att/ast/pull/1024

src/cmd/ksh93/bltins/trap.c:
- Use the normal method of parsing options with optget to fix the
  suspend builtin's test failure.

src/cmd/ksh93/tests/builtins.sh:
- Add the ksh2020 regression test for getting the usage information
  of each builtin. Enable all /opt/ast/bin builtins in a subshell
  since those should be tested as well (aside from getconf and uname
  because those builtins fallback to the real commands on error).

src/cmd/ksh93/tests/builtins.sh

@@ -885,5 +885,16 @@ fi
 EOF
 "$SHELL" -i "$sleepsig" 2> /dev/null || err_exit "'sleep -s' doesn't work with intervals of more than 30 seconds"
 
+# ==========
+# Builtins should handle unrecognized options correctly
+(
+	builtin $(builtin -l | awk -F "/" '/\/opt/ {print $5}') # Load all /opt/ast/bin builtins
+	for name in $(builtin -l | grep -Ev '(echo|/opt|test|true|false|getconf|uname|\[|:)'); do
+	    actual="$($name --this-option-does-not-exist 2>&1)"
+	    expect="Usage: $name"
+	    [[ $actual =~ $expect ]] || err_exit "$name should show usage info on unrecognized options (expected $(printf '%q' "$expect"), got $(printf '%q' "$actual"))"
+	done
+)
+
 # ======
 exit $((Errors<125?Errors:125))