as const.

without this the ASIO exception could be propagated due to (e.g.) too long
file name, which would subsequently shut down b10-auth.

Conflicts:
	ChangeLog

reviewed on jabber

details.  This should solve failure of some AXFR tests using SQLite3 on
some systems.

redundant 'pass'

to avoid duplicates.

counted twice.

section.  also extended tests to check the length the actual wire format
data for some specific cases.

account the DNS header size.  also added consideration for very large RRs
that would not even fit a single DNS message.

(I thought I did it in the IXFR tasks, but maybe I forgot to commit/push
that part)

- len() returns now uint16_t type
- using pre-increment intead of post-increment
- using distance() function
- moved some simple implementation to header

It is already the 29th in some parts of the world.

See ticket #1430 for more details. (Ticket pending tests before closing.)