bump internal libast version; various minor cleanups

These are minor things I accumulated over the last month or so.

Notable changes:

src/lib/libast/features/api,
src/lib/libast/misc/state.c,
src/lib/libast/comp/conf.tab,
src/cmd/ksh93/include/defs.h:
- Bump internal libast version to 20220101L. We've made a few
  additions to the API, at least pathicase (see 71934570, ca3ec200)
  and astconf_long (see c2ac69b2), so this should have been done
  already. This also updates '/opt/ast/bin/getconf _AST_VERSION'.
- Use AST_VERSION instead of outdated _AST_VERSION.
- In state.c, use AST_VERSION instead of hardcoding the version.

src/cmd/ksh93/sh/xec.c:
- Remove 'restorefd' variable, unused as of 42becab6.
- Remove 'cmdrecurse' function and SH_RUNPROG macro; this was once
  used by a few libcmd commands, but ast-open-archive reveals it's
  unused as of ast 1999-12-25.

src/cmd/ksh93/sh/*.c:
- Where available, use e_dot instead of "." for consistency; it is
  defined as an extern so we might as well use it.

src/cmd/ksh93/tests/*.sh:
- When reporting signal names in fails, include the SIG prefix.
- Fix a broken process hang test in subshell.sh.

src/lib/libast/man/sfdisc.3:
- Removed. The interfaces described here never made it out of AT&T;
  they do not exist in any libast version in ast-open-archive.
  Resolves: https://github.com/ksh93/ksh/issues/426

src/cmd/ksh93/tests/subshell.sh

@@ -551,11 +551,16 @@ $SHELL <<- \EOF
 		print -u2 done
 	}
 	out=$(eval "foo | cat" 2>&1)
-	(( ${#out} == 96011 )) || err_exit "\${#out} is ${#out} should be 96011"
+	print "${#out}" >out
 EOF
 } & pid=$!
-$SHELL -c "{ sleep .4 && kill $pid ;}" 2> /dev/null
-(( $? == 0 )) &&  err_exit 'process has hung'
+(sleep 4; kill -s KILL "$pid" 2>/dev/null) &	# another bg job to kill frozen test job
+{ wait "$pid"; } 2>/dev/null			# get job's exit status, suppressing signal messages
+if	((!(e = $?)))
+then	[[ $(<out) == '96011' ]] || err_exit "\${#out} is $(printf %q "$(<out)"), should be 96011"
+else	err_exit "process has hung (got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))"
+fi
+kill "$!" 2>/dev/null				# kill sleep process
 
 {
 x=$( $SHELL  <<- \EOF
@@ -848,7 +853,7 @@ test_pid=$!
 (sleep 10; kill -s KILL "$test_pid" 2>/dev/null) &	# another bg job to kill frozen test job
 sleep_pid=$!
 { wait "$test_pid"; } 2>/dev/null			# get job's exit status, suppressing signal messages
-((!(e = $?))) || err_exit "backtick comsub crash/freeze (got status $e$( ((e>128)) && print -n / && kill -l "$e"))"
+((!(e = $?))) || err_exit "backtick comsub crash/freeze (got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))"
 kill "$sleep_pid" 2>/dev/null
 
 # ======
@@ -858,7 +863,7 @@ test_pid=$!
 (sleep 2; kill -s KILL "$test_pid" 2>/dev/null) &
 sleep_pid=$!
 { wait "$test_pid"; } 2>/dev/null
-((!(e = $?))) || err_exit "backtick comsub hang (got status $e$( ((e>128)) && print -n / && kill -l "$e"))"
+((!(e = $?))) || err_exit "backtick comsub hang (got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))"
 kill "$sleep_pid" 2>/dev/null
 
 # Backtick command substitution with pipe hangs when filling out pipe buffer (rhbz#1138751)
@@ -867,7 +872,7 @@ test_pid=$!
 (sleep 2; kill -s KILL "$test_pid" 2>/dev/null) &
 sleep_pid=$!
 { wait "$test_pid"; } 2>/dev/null
-((!(e = $?))) || err_exit "backtick comsub with pipe hangs (got status $e$( ((e>128)) && print -n / && kill -l "$e"))"
+((!(e = $?))) || err_exit "backtick comsub with pipe hangs (got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))"
 kill "$sleep_pid" 2>/dev/null
 
 # ======
@@ -924,7 +929,7 @@ cat >$tmp/crash_rhbz1117404.ksh <<-'EOF'
 EOF
 got=$( { "$SHELL" "$tmp/crash_rhbz1117404.ksh"; } 2>&1)
 ((!(e = $?))) || err_exit 'crash while handling subshell trap' \
-	"(got status $e$( ((e>128)) && print -n / && kill -l "$e"), $(printf %q "$got"))"
+	"(got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"), $(printf %q "$got"))"
 
 # ======
 # Segmentation fault when using cd in a subshell, when current directory cannot be determined
@@ -941,14 +946,14 @@ got=$(set +x; { "$SHELL" -c '(subshfn() { bad; }; cd ..; echo "subPWD: $PWD"); t
 exp="PWD=$PWD"
 got=$(set +x; { "$SHELL" -c '(cd /; (cd /)); print -r -- "PWD=$PWD"'; } 2>&1)
 ((!(e = $?))) && [[ $got == "$exp" ]] || err_exit 'failed to restore nonexistent PWD on exiting a virtual subshell' \
-	"(got status $e$( ((e>128)) && print -n / && kill -l "$e"), $(printf %q "$got"))"
+	"(got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"), $(printf %q "$got"))"
 mkdir "$tmp/recreated"
 cd "$tmp/recreated"
 tmp=$tmp "$SHELL" -c 'cd /; rmdir "$tmp/recreated"; mkdir "$tmp/recreated"'
 exp="PWD=$PWD"
 got=$(set +x; { "$SHELL" -c '(cd /); print -r -- "PWD=$PWD"'; } 2>&1)
 ((!(e = $?))) && [[ $got == "$exp" ]] || err_exit 'failed to restore re-created PWD on exiting a virtual subshell' \
-	"(got status $e$( ((e>128)) && print -n / && kill -l "$e"), $(printf %q "$got"))"
+	"(got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"), $(printf %q "$got"))"
 cd "$tmp"
 
 # ======