* Add support for solaris

* Change state to handle system dependent termios type.
* Move syscalls to get and set termios to functions in files only built
  for respective platforms.
* Create `term_unix.go` go file built on all supported unices except
  solaris with types and functions valid for all of them.
* Change `MakeRaw` to set VMIN and VTIME to default values.

Fixes #95.

* Fix error handling

Doing the string comparison could be improved, but at least we should
return an error, if it is not "errno 0".