wlog: refactor wlcat mainly.
wlog: walb_util.hpp: refactor WalbSuperBlock.
wlog: walb_util.hpp: refactor remaining.
wlog: refactor bdiff, wlanalyze, wlinfo, wlupdate.
wlog: refactor wlgen.
wlog: refactor wlrestore.
wlog: use --verify option for test_wlog.sh.
wlog: refactor wlredo.
wlog: util.hpp: use uint64_t for device size.
wlog: wlredo: clip out-of-range IOs.
wlog: wlredo: support zero-discard.
bugfix: tool/trim.c: wrong arguments for discard ioctl.
wlog: wlredo: support discard.
wlog: test_wlog.sh: support zero-discard check.