I've created a patch  to fix swapped usage of idx_t and bm_word_t
The code currently uses a pointer to idx_t as an argument to
BitMap::set_map(bm_word_t* map) which fails on s390.
For most platforms the idx_t and bm_word_t types are effectively the
same, so the interchange is uncaught, but on s390 (32-bit) the size_t is
"unsigned long" which makes it incompatible with "unsigned int".