add ksh subshell support, but disabled in last chunk for
now to avoid a problem with zombies left behind.

https://midnight-commander.org/ticket/4447

Index: lib/shell.c
--- lib/shell.c.orig
+++ lib/shell.c
@@ -72,6 +72,8 @@ mc_shell_get_installed_in_system (void)
         mc_shell->path = g_strdup ("/bin/dash");
     else if (access ("/bin/busybox", X_OK) == 0)
         mc_shell->path = g_strdup ("/bin/busybox");
+    else if (access ("/bin/ksh", X_OK) == 0)
+        mc_shell->path = g_strdup ("/bin/ksh");
     else if (access ("/bin/zsh", X_OK) == 0)
         mc_shell->path = g_strdup ("/bin/zsh");
     else if (access ("/bin/tcsh", X_OK) == 0)
@@ -202,6 +204,13 @@ mc_shell_recognize_path (mc_shell_t * mc_shell)
         mc_shell->type = SHELL_BASH;
         mc_shell->name = "bash";
     }
+#if 0
+    else if (strstr (mc_shell->path, "/ksh") != NULL || getenv ("KSH_VERSION") != NULL)
+    {
+        mc_shell->type = SHELL_KSH;
+        mc_shell->name = "ksh";
+    }
+#endif
     else if (strstr (mc_shell->path, "/sh") != NULL || getenv ("SH") != NULL)
     {
         mc_shell->type = SHELL_SH;