header file cleanup

see http://seclists.org/nmap-dev/2013/q4/168

Move some includes out of nmap.h: nmap.h gets included lots of places,
and unconditionally included math.h, ctype.h, errno.h, stdio.h,
sys/stat.h, fcntl.h, sys/types.h, and stdarg.h. This commit moves those
includes into the .cc files where they are necessary and out of nmap.h

Remove redundant include global_structures.h, included from nmap.h

Removed redundant code included from nmap.h

Removing #include nbase.h when nmap.h is included (redundant)

Remove duplicate #include lines

Add ifndef guards to a few .h files

NmapOps.h

@@ -124,8 +124,10 @@
 
 /* $Id$ */
 
+#ifndef NMAPOPS_H
+#define NMAPOPS_H
+
 #include "nmap.h"
-#include "global_structures.h"
 #include "output.h"
 #include <nsock.h>
 #include <string>
@@ -424,4 +426,4 @@ class NmapOps {
   u8 spoof_mac[6];
   bool spoof_mac_set;
 };
-  
+#endif /* NMAPOPS_H */