Add a --debug flag for DEBUG builds

If you compile with:

  DEBUG=true rake build

then all the commands get a --debug flag as an option which will make
the server dump crazy amounts of data to stderr.

src/bitset.h

@@ -5,7 +5,6 @@
 #include <string.h>
 #include <pthread.h>
 
-#include "util.h"
 
 static inline char char_with_bit_set(int num) { return 1<<(num%8); }