Resizing of thread units on the run is not used nor endorsed,
as it's hard to guess when the specific threads terminate or not.
(They are allowed to run to the nearest cancellation point or finish.)

Closes #184

Conflicts:
	src/knot/main.c

Increase the expire time for zones with very short expiry. Without
this a zone may expire if there is a timeout, and once it has expired
it won't be served until it is refreshed. Sometimes, customers load
zones with SOA values that we have little control over.

Signed-off-by: Jan Kadlec <jan.kadlec@nic.cz>

Fix for a problem falling back to AXFR from IXFR when a single SOA
is processed only.

Signed-off-by: Jan Kadlec <jan.kadlec@nic.cz>

Allow the working directory to be set optionally with
knotd's -d option. The main purpose is to allow core dumps to go
somewhere other than '/'.

Signed-off-by: Jan Kadlec <jan.kadlec@nic.cz>

- Cleaned up some sem check functions - check level no longer needed,
  removed needless handler init parameters
- Added a better check for DNAME children error
- Sem. errors no longer ignored, will trigger bootstrap replan
- IXFR probably has its own checks, will inspect later
- Removed some weird assertions and philosophical questions in comments

Error message is already terminated by exclamation
mark. We cannot tell anything about data.