tmux: copy to X buffer for osx, add messages.

From "etc" repository:
=====================

commit 82df7c8f1d6a8dde29a7f3b648a5fd6d2ac69db0
Author: Azat Khuzhin <a3at.mail@gmail.com>
Date:   Fri Dec 28 23:13:58 2012 +0400

    tmux: remove file after copy
    tmux: fix save-buffer for osx (different tmux sessions.)

commit 41e20bb4614a618a626a54bf115299a0132ffcfd
Author: Azat Khuzhin <a3at.mail@gmail.com>
Date:   Fri Dec 28 23:09:06 2012 +0400

    tmux: add message "copied to clipboard"

commit 9410231bc18980514b26dac0c863062f1e08a1d5
Author: Azat Khuzhin <a3at.mail@gmail.com>
Date:   Fri Dec 28 23:05:20 2012 +0400

    tmux: drop deprecated config sections

commit 757fcdf336e32ff0390134fd3684a62554f5593a
Author: Azat Khuzhin <a3at.mail@gmail.com>
Date:   Fri Dec 28 23:00:22 2012 +0400

    tmux: osx copy to X buffer.