Follow grn_snip API change
Follow grn_snip API change

It requires Groonga 4.0.0. So we should update
required_groonga_version but we don't it yet. Because Groonga's
base_version isn't updated yet.

TODO: We should update required_groonga_version after Groonga's
version is 4.0.0.

mroonga/mroonga,yoku0825/mroonga,yoku0825/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga,mroonga/mroonga,naoa/mroonga,yoku0825/mroonga,yoku0825/mroonga,yoku0825/mroonga,mroonga/mroonga,naoa/mroonga,naoa/mroonga,mroonga/mroonga,naoa/mroonga