\itembreak, \itemjoin: Remove unused macros.

\itembreak, \itemjoin:	Remove unused macros.

\idxcode{}:  New macro; used to mark things that would be \code{} for entry
	into the index.  This allows easily switching things around for the
	font used in the index.  (O'Reilly seems to keep it all plain roman
	in the index.  Looks reasonable in the Python documentation as well.)

\*index{}:  Use \idxcode{} instead of {\codefont{}}.