All modules now have an 8-bit range for capability flags. Currently only
the client side authenticator and protocol capability bits are loaded due
to the fact that backend versions of these modules don't relate to a
particular service.
If a connection has not been fully established (i.e. authentication has
been completed) then it should not be considered as a connection pool
candidate.
Better to use types whose size is unquestionably unambiguous
in plugin interfaces.
As on current platforms sizeof(int32_t) == sizeof(int) plugins
need not immediately be changed to return int32_t:s instead of
int:s.
