add comments.
fix sector_compare().
fix sector_copy().
fix prototypes.
bugfix: realloc will not zero-clear additional memory in sector_array_realloc().
fix: restricted scope.
bugfix: use sect_ary->sector_size instead of sect_ary->array[0]->size.
a bit refactor.
fix: use memset.
fix: should be const.
use better algorithm for walb_bitmap_is_all_on().
fix: for better struct alignment.
fix bitmap.h.
fix: do not use gnu extension inside for statement.
a bit fix bitmap.h.
use is_same_snapshot_name() instead of compare_snapshot_name().
use is_same_sector() instead of sector_compare().
refactor: bit operations for u32 and u64.
add a comment for checksum rule.
fix: zero-clear before set name to superblock.