Eliminate sim_client include of getopt.h

Commit 9139a60 added an unconditional
include of getopt.h, which is non-portable (it isn't present on HP-UX)
and unecessary for getopt().  The same commit also disabled the
include of unistd.h (which is necessary for getopt()), as sim_client
no longer indirectly includes autoconf.  Make the unistd.h include
unconditional and remove the getopt.h include.

[ghudson@mit.edu: edited commit message]

ticket: 9102 (new)
tags: pullup
target_version: 1.21-next

src/appl/simple/client/sim_client.c

@@ -39,10 +39,7 @@
 #include <string.h>
 #include <errno.h>
 #include <netdb.h>
-#include <getopt.h>
-#ifdef HAVE_UNISTD_H
 #include <unistd.h>
-#endif
 
 #include "simple.h"