Change CBL_Replicator progress notification postingStyle to NSPostASAP

This will deliver progress information more quickly.
Fixes #396
Use more-correct code to dynamically dispatch to handler method in CBL_Router

Technique described at: http://stackoverflow.com/questions/7017281
This might fix a reported crash handling a GET request in 64-bit iOS (#360)

Conflicts:
	Source/CBL_Router.m