Fix library path for libpq on Windows.

Fixes #5066
Implement debug visualizers for Visual Studio.

Fixes #5067
Improve VS visualizers.

Refs #5067
Fix unit tests on Windows.

Fixes #5068
Move EmptyTimePeriod and EvenMinutesTimePeriod to libmethods.

Fixes #5032
Implement support for CRLs.

Fixes #3657
Fix compatibility with OpenSSL <1.0.0.

Refs #3657
Remove inconsistent Changelog from spec.
Fix BIO_f_zlib detection.

Fixes #5019
Remove quotes from perfdata keys.

Fixes #5031
Update migration script README.
Livestatus: Fix invalid livestatus query crashes Icinga 2.

Fixes #5076
Use a separate thread pool for checks.

Refs #5050
Include thread pool ID in debug messages.

Refs #5050
Create new threads more aggressively right after program start.

Refs #5050
Use normal check interval for services which haven't been checked yet.

Refs #5050
Don't kill too many worker threads at once.

Refs #5050
Set NPROC limit in the init script.

Refs #5050
Fix latency calculation.

Refs #5050
Merge branch 'feature/threadpool-bug-5050' into next

Fixes #5050