- Merged more OpenBSD changes:

 - Merged more OpenBSD changes:
   - [atomicio.c authfd.c scp.c serverloop.c ssh.h sshconnect.c sshd.c]
     move atomicio into it's own file.  wrap all socket write()s which
     were doing write(sock, buf, len) != len, with atomicio() calls.
   - [auth-skey.c]
     fd leak
   - [authfile.c]
     properly name fd variable
   - [channels.c]
     display great hatred towards strcpy
   - [pty.c pty.h sshd.c]
     use openpty() if it exists (it does on BSD4_4)
   - [tildexpand.c]
     check for ~ expansion past MAXPATHLEN
 - Modified helper.c to use new atomicio function.
 - Reformat Makefile a little
 - Moved RC4 routines from rc4.[ch] into helper.c
 - Added autoconf code to detect /dev/ptmx (Solaris) and /dev/ptc (AIX)