ksh(1): manual says $PPID is read-only

[Anthony Coulter]

The ksh(1) manual says that PPID should be read-only. But:

        $ man ksh | grep PPID     
          PPID       The process ID of the shell's parent (read-only).
        $ echo ${PPID}
        5967
        $ PPID=123
        $ echo ${PPID}
        123

We can fix either the manual or ksh itself; this diff takes the latter
approach. It is tempting to do this with "typeset -ir PPID" but that
actually doesn't work:

        $ FOO=123
        $ typeset -ir FOO
        ksh: FOO: is read only

So we fix this by putting "typeset -r PPID" on its own line. One could
imagine shortening the section below with something like:

        "typeset", "-i", "PPID", "OPTIND=1", NULL,
        "typeset", "-r", "KSH_VERSION", "PPID", NULL,
        "typeset", "-x", "SHELL", "PATH", "HOME", NULL,

but that involves some reordering: the -i's MUST come before the -r's.

Index: bin/ksh/main.c
===================================================================
RCS file: /open/anoncvs/cvs/src/bin/ksh/main.c,v
retrieving revision 1.79
diff -u -p -r1.79 main.c
--- main.c      4 Mar 2016 15:11:06 -0000       1.79
+++ main.c      8 Sep 2016 13:17:29 -0000
@@ -85,6 +85,7 @@ static const char *initcoms [] = {
        "typeset", "-r", "KSH_VERSION", NULL,
        "typeset", "-x", "SHELL", "PATH", "HOME", NULL,
        "typeset", "-i", "PPID", NULL,
+       "typeset", "-r", "PPID", NULL,
        "typeset", "-i", "OPTIND=1", NULL,
        "eval", "typeset -i RANDOM MAILCHECK=\"${MAILCHECK-600}\" 
SECONDS=\"${SECONDS-0}\" TMOUT=\"${TMOUT-0}\"", NULL,
        "alias",