sim: drop unused headers

These look like left over hacks from the days where we had to protect
ourselves from the compiler and C library.  None of these checks are
relevant, and we have common configure logic to do header tests.  Punt
them all now.

sim/microblaze/interp.c

@@ -18,10 +18,11 @@
 
 #include "config.h"
 #include <signal.h>
-#include "sysdep.h"
+#include <stdlib.h>
+#include <string.h>
 #include <sys/times.h>
 #include <sys/param.h>
-#include <netinet/in.h>	/* for byte ordering macros */
+#include <unistd.h>
 #include "bfd.h"
 #include "gdb/callback.h"
 #include "libiberty.h"