Add illumos support

[papertigers]

While trying to build bat on a SmartOS system, I found that termios currently doesn't support illumos.

root - rustdev ~/src/termios-rs (git:mz-illumos) # cargo test
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running target/debug/deps/termios-e986a12baa34d741

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests termios

running 10 tests
test src/lib.rs -  (line 44) ... ok
test src/lib.rs -  (line 19) ... ok
test src/lib.rs - Termios (line 152) ... ok
test src/lib.rs -  (line 78) ... ok
test src/lib.rs -  (line 28) ... ok
test src/lib.rs - cfsetspeed (line 361) ... ok
test src/lib.rs - cfgetispeed (line 221) ... ok
test src/lib.rs - cfgetospeed (line 236) ... ok
test src/lib.rs - cfsetispeed (line 278) ... ok
test src/lib.rs - cfsetospeed (line 321) ... ok

test result: ok. 10 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

This should support other Solaris based systems, but I sourced all of the header translations from illumos and I am unable to test on Oracle Solaris. Also I would have just named the target "illumos", but this issue is still being sorted out.

[papertigers]

Wondering if anyone has had a chance to look at this yet..

[papertigers]

@dcuddeback any chance you could look at / merge this?

[papertigers]

Just want to bump this PR again in hopes that it can get merged and I can remove the following from a bunch of local checkouts:

[patch.crates-io]
termios = { git = "https://github.com/papertigers/termios-rs/", branch = "mz-illumos" }

[dcuddeback]

Sorry for the long wait time, and thank you everyone for your patience. I've been on hiatus from open source work for a while. And thanks @papertigers for sending in the patch.

I've merge this on the command-line with some changes (ecbab66):

• Added extern "C" and #[no_mangle] for cfmakeraw() and cfsetspeed() to make them indistinguishable from C functions.
• Added a bunch of missing c_oflag and c_cflag bits.
• Dropped B7200, B14400, and B28800. I don't see those in /usr/include/sys/termios.h on OmniOS and I get a compile error when trying to use those in a C program.

I'm not familiar with illumos. If there's something wrong with the changes I made, someone please let me know. I get the impression that there are many different flavors of illumos, similar to how there are many distributions of Linux. I compared this PR against headers from OmniOS Community Edition (I installed the system/headers package).

If there are no issues, I'll cut a release to Cargo after I land the other open PRs.