[syslinux] Return from syslinux_local_boot(), syslinux_run_command() and syslinux_boot_linux()

[Sebastian Herbszt]

gfxboot uses those three calls, but currently doesn't really handle returns from them.
syslinux_boot_linux (lib/syslinux/load_linux.c) can return ("bail" label).
syslinux_local_boot (lib/syslinux/localboot.c) has a comment which says "returns
only on failure". The documentation for "Local boot" in doc/comboot.txt says "Does
not return". Which is correct?

syslinux_run_command (lib/syslinux/run_command.c) should not return according to
the comment in the source file. This seems compliant with the documentation of "Run
command" in doc/comboot.txt.

Can i assume gfxboot only needs to handle returns from syslinux_boot_linux() ?

Sebastian