[syslinux] Handling error scenarios in the core

[Gene Cumm]

With my recent work on UI/DEFAULT, I've been hunting around in the
core code to find any other locations that this new usage would be
useful.  As a result, I've come up with a few questions.

1) core/com32.inc: not_com32r jumps to enter_command.  Should it do
something based on ONERROR?

2) core/comboot.inc: comboot_bogus_tail and comboot_too_large go to
enter_command.  Again, use ONERROR?

There may be more that I'm missing.  I know bad_implicit/bad_kernel
and error_or_command (from abort_load) already use it.  I know
abort_check (executed with user input) does not but this one make a
lot of sense as it's not a system error.

3) core/ui.inc and core/abort.inc: bad_implicit/bad_kernel is silent
if there's an ONERROR but any other function that calls abort_load is
not.  Is this the desired behavior?

-- 
-Gene