message: Build: Include limits.h in bignum header
  Some systems won't have CHAR_BIT defined without explicitely including
  this.
diff: #define BITCOIN_BIGNUM_H
  #if defined HAVE_CONFIG_H
  -#include "pivx-config.h"
  +#include "config/pivx-config.h"
  #endif
  #include <stdexcept>
  #include <vector>
  +#include <limits.h>
  #if defined(USE_NUM_GMP)
  #include <gmp.h>
  #endif
  