The logger class constructor registers itself with the logger registry,
in order to enable dynamically setting log levels. However, since
thread_local variables may be (and are) initialized at the time of first
use, when the program starts up no loggers are registered.
Fix by making loggers global, not thread_local. This requires that the
registry use locking to prevent registration happening on different threads
from corrupting the registry.
Note that technically global variables can also be initialized at the
point of first use, and there is no portable way for classes to self-register.
However this is the best we can do.
To prepare a user-defined type, we need to look up its name in the keyspace.
While we get the keyspace name as an argument to prepare(), it is useless
without the database instance.
Fix the problem by passing a database reference along with the keyspace.
This precolates through the class structure, so most cql3 raw types end up
receiving this treatment.
Origin gets along without it by using a singleton. We can't do this due
to sharding (we could use a thread-local instance, but that's ugly too).
Hopefully the transition to a visitor will clean this up.
