(cherry picked from commit 3f32b2ea)

Previous URL was not available. Replace it with available URL. It is probably better to host this file by ourselves. Otherwise this link will be broken again in near future.
(cherry picked from commit 8d7c5d62)

Also, allows providing mroonga with a different soname.

A better implementation would be at libslap level (so that it works for
slapconsole too, for example), but requires too ugly hacks to accomodate
current data structure compared to change's otherwise (lack of) complexity.

It was reintroduced by a nightmarish merge: 42cfacae .

(cherry picked from commit 13fce878)

Conflicts:
	stack/slapos.cfg