Remove a stray `#include <functional>` from hyper.h.

This seems to be causing `hookset` to use `std::function` instead of
`hr::function`. Removing this one line shrinks the normal hyperrogue
binary from 9695484 bytes to 9669956 bytes.

hyper.h

@@ -633,8 +633,6 @@ color_t darkena(color_t c, int lev, int a);
 
 static const int DISTANCE_UNKNOWN = 127;
 
-#include <functional>
-
 template<class T, class U> int addHook(hookset<T>*& m, int prio, const U& hook) {
   if(!m) m = new hookset<T> ();
   while(m->count(prio)) {