[syslinux] Avoid returning to menu if boot error happened

[Anatol Pomozov]

Hi

I have a weird early boot bug that most likely happens because of
interaction between syslinux (6.03pre18), btrfs and initram generated
by Linux Arch installer.

For some reason boot fails. Syslinux prints some information and
returns back to the menu. Unfortunately it clears all the messages
from screen. I really want to know what boot process prints there.

Looking at  com32/elflink/ldlinux/execute.c (I believe it is where the
error handled) I see the comment: /* If this returns, something went
bad; return to menu */

Would it be better avoid returning to menu in case of an error? I
think syslinux should print message "Press any key to return back to
menu". This will preserve the error messages needed during debugging.
What do you think?