build: include man/*.in to EXTRA_DIST

Currently, there will be an error in the distribution directory.
After a 'make clean', 'make' will fail becuase it cannot find *.in files in
directory 'man'.

This patch fixed this.

Signed-off-by: Kai Zhang <kyle@zelin.io>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
farm: remove unnecessary casting

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Add more macros for sha1.h

- use SHA1_DIGEST_SIZE instead of home-grew SHA1_LEN
- move snap_log into farm.h

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>