Bug 1577907

+++ This bug was initially created as a clone of Bug #1577902 +++

Reproducer:

1. Run the script
---8<---8<---
#!/bin/ksh
  
function  funcTERM
{
    exit 0
}
  
trap  funcTERM  SIGTERM
  
while true
do
    i=0
    while [ $i -lt 100 ]
    do
        DUMMY=`echo dummy`
        let ++i
    done
    ps u --no-headers -p $$ 
    sleep 0.1
done
---8<---8<---

2. Keep looking at 6th column(RSS) of ps
# ./check.ksh 
root      8643  0.0  0.3 109344  1668 pts/1    S+   13:19   0:00 /bin/ksh ./check.ksh
...
root      8643  4.2  0.4 109600  2136 pts/1    S+   13:19   0:00 /bin/ksh ./check.ksh
root      8643  4.3  0.4 109600  2148 pts/1    R+   13:19   0:00 /bin/ksh ./check.ksh
root      8643  4.3  0.4 109600  2148 pts/1    S+   13:19   0:00 /bin/ksh ./check.ksh

Minimal patch to correct the problem:
"""
diff -up ksh-20120801/src/cmd/ksh93/sh/subshell.c.orig ksh-20120801/src/cmd/ksh93/sh/subshell.c
--- ksh-20120801/src/cmd/ksh93/sh/subshell.c.orig	2018-05-11 13:45:12.280999698 -0300
+++ ksh-20120801/src/cmd/ksh93/sh/subshell.c	2018-05-11 13:46:19.396000044 -0300
@@ -575,7 +575,7 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_
 		sp->coutpipe = shp->coutpipe;
 		sp->cpipe = shp->cpipe[1];
 		shp->cpid = 0;
-		sh_sigreset(0);
+		sh_sigreset(1);
 	}
 	jmpval = sigsetjmp(buff.buff,0);
 	if(jmpval==0)
"""

  The patch could be made a bit longer, but more complex, to avoid the strdup
calls that will be just released shortly after (with this patch).

** Note ** the equivalent patch is required in xec.c, but there is no reproducer
so far for the leak, that would happen in the same conditions (sh_sigreset zero'ing
the vector of strdup'ed strings).