Disable NSS Preprocessor definitions

-NSS, which is enabled by default, leads to crashes when logging in
-Disable for now so US/VN can build and run zChat
XMPP: Support SASL ANONYMOUS client auth mechanism

- Ref: XEP-0175

Issue CHAT-923
Merge pull request #1 from PersonifyInc/david.scherba-2014-05-08-chat-923

CHAT-923: XMPP support for SASL ANONYMOUS client authentication