Added protocol for srv lookups

More work on the blocking resolver

Implemented the idle "spawn" in LmBlockingResolver. In order to simulate the asynchronous API of LmResolver the synchronous LmBlockingResolver runs in an idle callback. That means the lm_resolver_lookup call will return just as it does in the asynchronous version and instead the result will come through the given callback.

Added LmBlockingResolver which will handle the case when we do not have libasyncns. The blocking resolver will be blocking while waiting for response from a web server.

Added LmAsyncnsResolver

Fixed some spaces

Added type property to LmResolver

Changed so that we create a resolver with various arguments depending on type. Instead of having the lookup_host and lookup_srv virtual methods there is now only one lookup method and the resolver is created using new_for_host or new_for_srv instead. The host or domain/srv values are set as properties on the base class for the sub classes to read out.

Made LmResolver an object for subclassing instead of an interface

Added LmResolver interface. The LmResolver interface will be implemented in one blocking fashion and one implementation that uses Libasyncns. Designing this as an interface will make it easy to implement an asynchronous version using platform specific technologies for Windows and Mac OS X. It will also make it easier to create a mock implementation to simulate various error codes to test the layers using the resolver.