- update to 2.2.9:
* {mount,umount}.nilfs2: use libmount by default
* fix build warnings in Autoconf 2.70 or later:
- configure.ac: use AC_CONFIG_HEADERS instead of AC_CONFIG_HEADER
- configure.ac: remove AC_PROG_CC_C99 macro
- configure.ac: use AC_USE_SYSTEM_EXTENSIONS instead of AC_GNU_SOURCE
- configure.ac: use LT_INIT instead of AC_PROG_LIBTOOL
- configure.ac: remove obsolete AC_HEADER_STDC marco
- configure.ac: remove obsolete AC_HEADER_TIME marco
- do not use AC_TYPE_SIGNAL and RETSIGTYPE
* fix gcc8 -Wstringop-truncation warnings:
- mkfs, nilfs-tune: fix gcc8 warnings for volume name buffers
- nilfs-tune: fix gcc8 warnings at user_string() and group_string()
* update documents:
- README: update git repository url
- README: alter URLs referenced in the developer notes
- README: remedy a note about dependency on the selinux library