Always explicitly name which arguments are non-null, even if all
arguments are non-null. This is to avoid bugs where newly added
arguments are automatically non-null by accident, possibly leading to
optimisation errors.
This also fixes a few potential errors related to non-null arguments;
specifically it prevents the compiler optimising away a test for sni
being NULL in cachedsess_mkkey().
Issue: #14
Reported by: kythyria
Yield the CPU in the main thread until the proxy thread manager is fully
started. Otherwise, the main thread could free the proxy thread manager
while the threads are still starting up, leading to a deadlock.
