JTermios OpenBSD Support

[nicholasburn]

This pull request will add OpenBSD support to JTermios

c-openbsd.c has been created by patching together the other c-*.c files
JTermiosImpl.java is a copy of the freebsd's one using platform specific values for the constants
JTermios.java has been edited in a self explanatory way

TestSuite.java passes all tests (using an emulated serial port with socat)
TwoPortSerialTest.java hasn't been tried because I don't understand what that is

I'm making this request because intellij idea's terminal plugin is not working and the log says "JTermios has no support for OS OpenBSD"

Thank you and have a good day

[nicholasburn]

I have force-pushed in the forked repository in order to delete a commit that I have made by mistake.
I think it should not be a problem for the pull request, but if you want I can close this and open a new one, just to be sure not to delete anything else.