Remove unnecessary type casts of printf arguments to unsigned long

Remove unnecessary type casts of printf arguments to unsigned long
(code refactoring)

* alloc.c [!NO_DEBUGGING] (GC_print_heap_sects): Remove unnecessary
cast to unsigned long in GC_*_printf call and adjust printf format
specifier to match the argument type.
* checksums.c [CHECKSUMS] (GC_checksum): Likewise.
* mark.c [PARALLEL_MARK] (GC_mark_local): Likewise.
* tests/test.c (typed_test): Likewise.
* checksums.c [CHECKSUMS] (GC_checksum): Change type of GC_n_clean,
GC_n_dirty from int to unsigned long.