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

tcpip.h

@@ -129,78 +129,7 @@
 #ifndef TCPIP_H
 #define TCPIP_H
 
-#ifdef HAVE_CONFIG_H
-#include "nmap_config.h"
-#endif
-
-#include "nbase.h"
-
-#ifdef WIN32
-#include "mswin32\winclude.h"
-#else
-
-#ifdef STDC_HEADERS
-#include <stdlib.h>
-#else
-void *malloc();
-void *realloc();
-#endif
-
-#if STDC_HEADERS || HAVE_STRING_H
-#include <string.h>
-#if !STDC_HEADERS && HAVE_MEMORY_H
-#include <memory.h>
-#endif
-#endif
-#if HAVE_STRINGS_H
-#include <strings.h>
-#endif
-
-#ifdef HAVE_BSTRING_H
-#include <bstring.h>
-#endif
-
-#include <ctype.h>
-#include <sys/types.h>
-
-#ifdef HAVE_SYS_PARAM_H
-#include <sys/param.h> /* Defines MAXHOSTNAMELEN on BSD*/
-#endif
-
-#include <stdio.h>
-
-#if HAVE_NETINET_IN_H
-#include <netinet/in.h>
-#endif
-
-#ifdef HAVE_RPC_TYPES_H
-#include <rpc/types.h>
-#endif
-
-#ifdef HAVE_NETDB_H
-#include <netdb.h>
-#endif
-
-#if HAVE_SYS_SOCKET_H
-#include <sys/socket.h>
-#endif
-
-#include <arpa/inet.h>
-#if HAVE_UNISTD_H
-#include <unistd.h>
-#endif
-#include <fcntl.h>
-
-#if TIME_WITH_SYS_TIME
-# include <sys/time.h>
-# include <time.h>
-#else
-# if HAVE_SYS_TIME_H
-#  include <sys/time.h>
-# else
-#  include <time.h>
-# endif
-#endif
+#include "nmap.h"
 
 #include <sys/ioctl.h>
 
@@ -215,17 +144,14 @@ extern "C" {
 #if HAVE_SYS_SOCKIO_H
 #include <sys/sockio.h>  /* SIOCGIFCONF for Solaris */
 #endif
-#endif /* WIN32 */
 
 #include <setjmp.h>
 #include <errno.h>
 #include <signal.h>
 #include <dnet.h>
 
-
-
-#include "nmap.h"
-#include "global_structures.h"
+/* from Target.h */
+class Target;
 
 #ifndef INET_ADDRSTRLEN
 #define INET_ADDRSTRLEN 16