fix: the monster build

It was broken in two places:
* there was a missing header file (008097b);
* a couple of variables were declared inside a `case` statement without
  a scope (abc8f7a).

crawl-ref/source/util/monster/monster-main.cc

@@ -12,6 +12,7 @@
 #include "fight.h" // spines_damage
 #include "item-name.h"
 #include "item-prop.h"
+#include "items.h"
 #include "los.h"
 #include "mapdef.h" // item_list
 #include "message.h"
@@ -1026,10 +1027,13 @@ int main(int argc, char* argv[])
                         colour(YELLOW, damage_flavour("acid", "4d3"));
                     break;
                 case AF_AIRSTRIKE:
+                {
                     short int min = pow(hd, 1.33) / 2;
                     short int max = pow(hd + 1, 1.33) * 11 / 6;
                     monsterattacks +=
                         colour(LIGHTBLUE, damage_flavour("airstrike", min, max));
+                    break;
+                }
                 case AF_BLINK:
                     monsterattacks += colour(MAGENTA, "(blink self)");
                     break;