SHOPT_SPAWN: rm unused job control code (re: f207cd5, 41ebb55)

Since f207cd5, sh_ntfork() is never called if job.jobcontrol is
set (i.e. if job control is active on an interactive shell), so the
code that is only run if job.jobcontrol is set should be removed.

src/cmd/ksh93/sh/xec.c:
- Remove spawnveg() define that is unused as of 7b0e077.
- sh_exec(): Simplify SHOPT_SPAWN preprocessor logic. As sh_fork()
  never returns a negative value, only run the parent<0 check after
  running sh_ntfork() -- that check already didn't happen when
  compiling ksh with SHOPT_SPAWN disabled.
- sh_ntfork(): Remove signal and terminal handling (with race
  condition) that was only run with job.jobcontrol set.

src/cmd/ksh93/sh/xec.c

@@ -57,9 +57,6 @@
 #if _lib_nice
     extern int	nice(int);
 #endif /* _lib_nice */
-#if !_lib_spawnveg
-#   define spawnveg(a,b,c,d)    spawnve(a,b,c)
-#endif /* !_lib_spawnveg */
 #if SHOPT_SPAWN
     static pid_t sh_ntfork(Shell_t*,const Shnode_t*,char*[],int*,int);
 #endif /* SHOPT_SPAWN */
@@ -1624,22 +1621,20 @@ int sh_exec(register const Shnode_t *t, int flags)
 #endif
 #if SHOPT_SPAWN
 				if(com && !job.jobcontrol)
-					parent = sh_ntfork(shp,t,com,&jobid,ntflag);
-				else
-					parent = sh_fork(shp,type,&jobid);
-				if(parent<0)
 				{
-					/* prevent a file descriptor leak from a 'not found' error */
-					if(shp->topfd > topfd)
-						sh_iorestore(shp,topfd,0);
-
-					if(shp->comsub==1 && usepipe && unpipe)
-						sh_iounpipe(shp);
-					break;
+					parent = sh_ntfork(shp,t,com,&jobid,ntflag);
+					if(parent<0)
+					{
+						if(shp->topfd > topfd)
+							sh_iorestore(shp,topfd,0);  /* prevent FD leak from 'not found' */
+						if(shp->comsub==1 && usepipe && unpipe)
+							sh_iounpipe(shp);
+						break;
+					}
 				}
-#else
-				parent = sh_fork(shp,type,&jobid);
+				else
 #endif /* SHOPT_SPAWN */
+					parent = sh_fork(shp,type,&jobid);
 			}
 			if(job.parent=parent)
 			/* This is the parent branch of fork
@@ -1735,7 +1730,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 				}
 				sh_offstate(SH_INTERACTIVE);
 				/* pipe in or out */
-#ifdef _lib_nice
+#if _lib_nice
 				if((type&FAMP) && sh_isoption(SH_BGNICE))
 					nice(4);
 #endif /* _lib_nice */
@@ -3500,7 +3495,7 @@ static void sigreset(Shell_t *shp,int mode)
 
 /*
  * A combined fork/exec for systems with slow fork().
- * Note: Incompatible with job control.
+ * Incompatible with job control on interactive shells (job.jobcontrol).
  */
 static pid_t sh_ntfork(Shell_t *shp,const Shnode_t *t,char *argv[],int *jobid,int flag)
 {
@@ -3509,7 +3504,7 @@ static pid_t sh_ntfork(Shell_t *shp,const Shnode_t *t,char *argv[],int *jobid,in
 	static int	savejobid;
 	struct checkpt	*buffp = (struct checkpt*)stkalloc(shp->stk,sizeof(struct checkpt));
 	int		otype=0, jmpval,jobfork=0;
-	volatile int	jobwasset=0, scope=0, sigwasset=0;
+	volatile int	scope=0, sigwasset=0;
 	char		**arge, *path;
 	volatile pid_t	grp = 0;
 	Pathcomp_t	*pp;
@@ -3577,17 +3572,8 @@ static pid_t sh_ntfork(Shell_t *shp,const Shnode_t *t,char *argv[],int *jobid,in
 		}
 		arge = sh_envgen();
 		shp->exitval = 0;
-#ifdef SIGTSTP
-		if(job.jobcontrol)
-		{
-			signal(SIGTTIN,SIG_DFL);
-			signal(SIGTTOU,SIG_DFL);
-			signal(SIGTSTP,SIG_DFL);
-			jobwasset++;
-		}
-#endif /* SIGTSTP */
 #ifdef JOBS
-		if(sh_isstate(SH_MONITOR) && (job.jobcontrol || (otype&FAMP)))
+		if(sh_isstate(SH_MONITOR) && (otype&FAMP))
 		{
 			if((otype&FAMP) || job.curpgid==0)
 				grp = 1;
@@ -3643,17 +3629,6 @@ static pid_t sh_ntfork(Shell_t *shp,const Shnode_t *t,char *argv[],int *jobid,in
 	sh_popcontext(shp,buffp);
 	if(buffp->olist)
 		free_list(buffp->olist);
-#ifdef SIGTSTP
-	if(jobwasset)
-	{
-		signal(SIGTTIN,SIG_IGN);
-		signal(SIGTTOU,SIG_IGN);
-		if(sh_isstate(SH_INTERACTIVE))
-			signal(SIGTSTP,SIG_IGN);
-		else
-			signal(SIGTSTP,SIG_DFL);
-	}
-#endif /* SIGTSTP */
 	if(sigwasset)
 		sigreset(shp,1);	/* restore ignored signals */
 	if(scope)
@@ -3673,13 +3648,6 @@ static pid_t sh_ntfork(Shell_t *shp,const Shnode_t *t,char *argv[],int *jobid,in
 #ifdef JOBS
 		if(grp==1)
 			job.curpgid = spawnpid;
-#   ifdef SIGTSTP
-		if(job.jobcontrol && grp>0 && !(otype&FAMP))
-		{
-			while(tcsetpgrp(job.fd,job.curpgid)<0 && job.curpgid!=spawnpid)
-				job.curpgid = spawnpid;
-		}
-#   endif /* SIGTSTP */
 #endif /* JOBS */
 		savejobid = *jobid;
 		if(otype)