do not resend signal on termination (rhbz#1075635)

public bug: https://bugzilla.redhat.com/1075635
patched by: https://src.fedoraproject.org/rpms/ksh/blob/642af4d6/f/ksh-20120801-sufix.patch

src/cmd/ksh93/sh/io.c: io_prompt():
- Reset the currently running command's exit status (exitval) when
  writing the prompt. This does not affect "$?" which is savexit.

src/cmd/ksh93/sh/io.c

@@ -2096,6 +2096,7 @@ static int	io_prompt(Shell_t *shp,Sfio_t *iop,register int flag)
 			}
 #endif	/* TIOCLBIC */
 			cp = sh_mactry(shp,nv_getval(sh_scoped(shp,PS1NOD)));
+			shp->exitval = 0;
 			for(;c= *cp;cp++)
 			{
 				if(c==HIST_CHAR)