Adding termios.h to openbsd headers.

Attempting to correct for conflicting defines from `rpcsvc/rex.h`

Author: berkowski

libc-test/build.rs

@@ -206,6 +206,7 @@ fn main() {
     if openbsd {
         cfg.header("ufs/ufs/quota.h");
         cfg.header("rpcsvc/rex.h");
+        cfg.header("termios.h");
         cfg.header("pthread_np.h");
         cfg.header("sys/syscall.h");
     }