Look out, world, here comes the Nmap massping migration!

This is the merging of the code that was previously in
/nmap-exp/david/nmap-massping-migration. These are all the big changes
that get rid of massping in favor of doing host discovery using
ultra_scan.

For now, there is a toggle that turns these new changes off. Undefine
NEW_MASSPING in targets.cc to go back to the old code. All of that will
be deleted eventually.

There are likely a few more changes that will be made to this system in
the near future. Those will be made in
/nmap-exp/david/nmap-massping-migration and merged back.

Don't release this just yet, because I'm going to make a few more
commits real quick to remove some debugging stuff.

(Note to self: this merge back was from r5693 in
/nmap-exp/david/nmap-massping-migration.)

nmap.h

@@ -333,6 +333,7 @@ void *realloc();
 #define UC(b)   (((int)b)&0xff)
 #define SA    struct sockaddr  /*Ubertechnique from R. Stevens */
 
+#define HOST_UNKNOWN 0
 #define HOST_UP 1
 #define HOST_DOWN 2 
 #define HOST_FIREWALLED 4 
@@ -346,7 +347,7 @@ void *realloc();
 #define PINGTYPE_TCP  16
 #define PINGTYPE_TCP_USE_ACK 32
 #define PINGTYPE_TCP_USE_SYN 64
-#define PINGTYPE_RAWTCP 128
+/* # define PINGTYPE_RAWTCP 128 used to be here, but was never used. */
 #define PINGTYPE_CONNECTTCP 256
 #define PINGTYPE_UDP  512
 #define PINGTYPE_ARP 1024