Kill termio.h and sys/termios.h

On FreeBSD, compilation complains that "this file includes
<sys/termios.h> which is deprecated, use <termios.h> instead". On Linux
and FreeBSD, <sys/termios.h> literally just pulls in <termios.h>. On OS
X and Solaris, <termios.h> pulls in <sys/termios.h>.

<termio.h> doesn't exist on FreeBSD or Mac OS X, and on Linux is marked
as deprecated and just includes <termios.h>. It does exist on Solaris,
but no `struct termio` is ever actually used in the codebase.