This fix:
* Ensures the user library accesses the correct ServerHooks
singleton object.
* Provides a way to initialize the BIND 10 logging framework in
the context of the user-written hooks library.
Absence of "libdl" on BSD systems required an addition to configure.ac
to check its presence. Problems with converting "pointer to object"
to "pointer to void*" via reinterpret_cast on Solaris required an
extension to the Pointer_converter class.