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- Use AST_VERSION instead of outdated _AST_VERSION.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/sh/path.c

@@ -319,7 +319,7 @@ static char *dotpaths_lib(Pathcomp_t *pp, char *path)
 	if(last)
 		*last = 0;
 	else
-		path = ".";
+		path = (char*)e_dot;
 	r = stat(path,&statb);
 	if(last)
 		*last = '/';
@@ -1671,7 +1671,7 @@ Pathcomp_t *path_addpath(Pathcomp_t *first, register const char *path,int type)
 		if(*cp==':')
 		{
 			if(type!=PATH_FPATH)
-				first = path_addcomp(first,old,".",type);
+				first = path_addcomp(first,old,e_dot,type);
 			while(*++path == ':');
 		}
 		else

src/cmd/ksh93/sh/xec.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1982-2012 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2021 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2022 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 1.0                  *
 *                    by AT&T Intellectual Property                     *
@@ -71,7 +71,6 @@ static void	coproc_init(int pipes[]);
 static void	*timeout;
 static char	nlock;
 static char	pipejob;
-static int	restorefd;
 
 struct funenv
 {
@@ -1325,7 +1324,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 							if(!sh.pwd)
 								path_pwd();
 							if(sh.pwd)
-								stat(".",&statb);
+								stat(e_dot,&statb);
 							sfsync(NULL);
 							share = sfset(sfstdin,SF_SHARE,0);
 							sh_onstate(SH_STOPOK);
@@ -1371,7 +1370,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 						bp->data = (void*)save_data;
 						if(sh.exitval && errno==EINTR && sh.lastsig)
 							sh.exitval = SH_EXITSIG|sh.lastsig;
-						else if(!nv_isattr(np,BLT_EXIT) && sh.exitval!=SH_RUNPROG)
+						else if(!nv_isattr(np,BLT_EXIT))
 							sh.exitval &= SH_EXITMASK;
 					}
 					else
@@ -1410,7 +1409,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 						if(sh.pwd)
 						{
 							struct stat stata;
-							stat(".",&stata);
+							stat(e_dot,&stata);
 							/* restore directory changed */
 							if(statb.st_ino!=stata.st_ino || statb.st_dev!=stata.st_dev)
 								chdir(sh.pwd);
@@ -1614,7 +1613,6 @@ int sh_exec(register const Shnode_t *t, int flags)
 				}
 #endif /* SHOPT_BGX */
 				nv_getval(RANDNOD);
-				restorefd = sh.topfd;
 				if(type&FCOOP)
 				{
 					pipes[2] = 0;
@@ -3409,20 +3407,6 @@ int sh_fun(Namval_t *np, Namval_t *nq, char *argv[])
 	return(sh.exitval);
 }
 
-/*
- * This dummy routine is called by built-ins that do recursion
- * on the file system (chmod, chgrp, chown).  It causes
- * the shell to invoke the non-builtin version in this case
- */
-int cmdrecurse(int argc, char* argv[], int ac, char* av[])
-{
-	NOT_USED(argc);
-	NOT_USED(argv[0]);
-	NOT_USED(ac);
-	NOT_USED(av[0]);
-	return(SH_RUNPROG);
-}
-
 /*
  * set up pipe for cooperating process 
  */