XMPPStreamStartTLSPolicy

Fixes #332
Prefered => Preferred to match Apple's naming conventions
Removed compiler warnings from unused xmpplog variables
Merge pull request #337 from jonasman/master

Removed compiler warnings from unused xmpplog variables
fixed compiler warnings, removed unused log variables 2
Merge pull request #338 from jonasman/master

fixed compiler warnings, removed unused log variables 2
Implemented SASL SCRAM-SHA-1 Authentication

RFC5802 http://tools.ietf.org/html/rfc5802

Support for SHA-1 but would be easy to support other hashing algorithms
in the future. Does not support channel binding.
Merge pull request #341 from ChatSecure/scram-sha1

Implemented SASL SCRAM-SHA-1 Authentication
XMPPMessageArchiving Default Log Level
Merge branch 'master' into release

Conflicts:
	Core/XMPPStream.h
	Core/XMPPStream.m
	Vendor/CocoaAsyncSocket