Expose signal value of siginfo_t

[DoumanAsh]

Currently exposes it for following platforms:

• Linux has it as enum _timer and it is exposed alongside sigval
• On FreeBSD like systems si_value follows after si_addr (according to headers)
• Darwin is similar to FreeBSD
• NetBSD and FreeBSD uses struct that contains pid, uid, and si_value. Exposed via it

P.s. I'd like to take a look at other platforms too, but these are what I know so far.
FreeBSD needs some testing though

cc @gnzlbg

[rust-highfive]

r? @gnzlbg

(rust_highfive has picked a reviewer for you, use r? to override)

[gnzlbg]

Thank you for the PR. Our CI is currently down because we are migrating to Azure Pipelines, but it looks good, I'll try to merge it this weekend.

[DoumanAsh]

Updated with other unix platforms.
I used publicly available repositories with source code as reference.
But I'm not sure how correct it is per se

[gnzlbg]

@bors: r+

[bors]

📌 Commit 2cd9b40 has been approved by gnzlbg

[bors]

⌛ Testing commit 2cd9b40 with merge 2a58378...

[gnzlbg]

@asomers @semarie this might need tweaking for OpenBSD, but it shouldn't break anything to land this - i'm not sure about NetBSD, but with this in master it should be easier to try this out, and improve this iteratively.

[bors]

💔 Test failed - checks-cirrus-freebsd-11

[asomers]

You need to double check the size of your pad fields. They aren't right for 64-bit FreeBSD.

[DoumanAsh]

Ok, I'll need to check it.
I was using signal.h as reference but i didn't exactly check every type inside.
Wonder if it is sigval union behaving

[gnzlbg]

It appears that the freebsd jobs are still failing.

[DoumanAsh]

@gnzlbg Yeah, before my traveling I actually was trying to fix MacOS tests, which are still failing for some reason.
But as for freebsd I'm not exactly sure even where it fails, so I'd need to take a look at how this error ouput gets generated

[gnzlbg]

you might just need to rebase on top of master, those error shouldn't be there, and don't appear related to this PR

[DoumanAsh]

Ok, done, I'll check it out once CI is finished

UPD: Removed pub from internal struct in apple module.
CI should be working now

[DoumanAsh]

@gnzlbg CI passed

[gnzlbg]

@bors: r+

[bors]

📌 Commit 0c2e783 has been approved by gnzlbg

[bors]

⌛ Testing commit 0c2e783 with merge 6307a0b...

[bors]

☀️ Test successful - checks-cirrus-freebsd-11, checks-cirrus-freebsd-12, checks-travis, status-appveyor
Approved by: gnzlbg
Pushing 6307a0b to master...