Add a way to exit GAP immediately, with an exit code.

[fingolfin]

Currently, I have to use IO_exit for that, but as was explained in #364, this is not so nice for various reasons.

Such a feature is very important if one wants to properly script running GAP computations. E.g. when building the manual, or running tests, being able to set an exit code in order to signal the build system that there was a failure.

[stevelinton]

Would it be enough to add a one-argument version of QUIT_GAP() and FORCE_QUIT_GAP()?

[ChrisJefferson]

Or, what's wrong with QUIT_GAP and FORCE_QUIT_GAP already? :) (you may have missed them being added).

[olexandr-konovalov]

@ChrisJefferson isnt' this something what you've done recently ?

[fingolfin]

Great! But I wasn't aware of it. I searched my email archive, I found an email by @ChrisJefferson from October 2014 that he wants to modify QUIT_GAP in that way. But I saw no further discussion, nor any description of this new feature in dev/Updates or any GAP release notes, i.e. it is not mentioned in chapter 2 of the GAP manual.

In fact, it doesn't seem to be documented at all: I just re-run make manuals, and it neither appears in the index, nor does the built-in help system know anything about it. Though I do see it being mentioned in doc/ref/mloop.xml. Huh?

[fingolfin]

Argh, never mind. For some really stupid reason, GAP picked up the manual from another, older GAP installation (a matter of a badly placed symlink). Fixed that, so now I see QUIT_GAP in all its glory in the manual.

Still think it would be nice to mention it in an dev/Updates note, though :)

[olexandr-konovalov]

BTW, PR #150 is marked for GAP 4.8.0 milestone.