Library for EMACS C mode

[David Eppstein <Eppstein@COLUMBIA-20.ARPA>]

I have created an EMACS library for C mode (and changed HAKLIB to use it).
So far this is only installed on Sierra, in EMACS:CMODE.*.
The code for tab is kind of ugly but it seems to work (at least for
the style of indentation I like; no hooks are provided to change the style).
Also included is a macro on C-M-* to create a block comment of the form
	/*
	** Comment
	** More comment
	*/
Tab or linefeed within such a comment will make more starred comment lines.
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