fix #3351

See https://github.com/randombit/botan/issues/1558

Also simplify how we did the whole “limit + 1”
And fix one bad interpretation of the XEP for the case where the query has
no after or before restriction.

fix #3349

fix #3343

This reverts commit 857c7d39.

This reverts commit 5ef7ba08.

This way, it works, whatever the order of insertion in the database was.

fix #3343

Some template specialization were not found, because they were not declared
at the point they were used.

We moved things around, things are less inter-dependant, and also now it
works.

PLEASE backup your database before testing this commit, and report any
migration issue.

In postgresql, we use timestamp with timezone.
In sqlite3 we use REAL (the date is expressed as julianday)

This requires a migration of the muclogline_ table:
In postgresql it’s pretty simple, we convert all the integer into timestamps

With sqlite3, we actually rename the table, create the new one with the
correct type, then copy everything to the new table, with a conversion
function for the Date_ column, and then we delete the old table.

fix #3343

fix #3347

(that is, from time to time, hope I won’t forget)

fix #3305

fix #3305

fix #3317

fix #3336

Instead, generate a uuid for that message

From XEP 0045:
“Note: the requirement to reflect the 'id' attribute was added in version
1.31 of this XEP. Servers following the new specification SHOULD advertise
that with a disco info feature of 'http://jabber.org/protocol/muc#stable_id'
on both the service domain and on individual MUCs, so that clients can check
for support.”

fix #3283