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.

Some style fixes

Refactored some of the SSL code in LmConnection. Added functions to wrap LmSSL functions in LmOldSocket to minimize the number of calls from LmConnection to LmSSL directly. Also split out function to register a STARTTLS handler if it is not already registered and we are using STARTTLS.

Moved the call to _lm_ssl_close to LmOldSocket

Split out old_socket_do_write from lm_old_socket_do_write. The reason for having the buffer setup split out of lm_old_socket_do_write was that it's also used internally in LmOldSocket. Split out the part that should not care about buffered output into old_socket_do_write. Also renamed lm_old_socket_do_write to lm_old_socket_write.

Some more cleanups

Moved the ifdefs for HAVE_ASYNCNS to the LmOldSocket code. This cleans up the code a bit as it leaves the ifdefs to internal in LmOldSocket.