Reduce memory usage when masking messages.

Avoid to copy the whole message two times in memory. It saves memory
(not able to measure) and also saves CPU (approximately 3 to 5%).
[auto] Merge from Websocket

    • #ef9e155 — Reduce memory usage when masking messages. (Ivan Enderlin, 2014-07-09)

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Merge branch 'master' of /var/lib/git/repositories/Library/Websocket