Revised ELI-style history option

Here's a new version of the Eli history option. This adds a pair of commands to cycle through the history *without* prefix-matching. It also turns *off* the Eli history option when cycling through history and prefix-matching.

Using the Eli history option, I bind the "no-match" variants to M-p and M-n and the matching variants to M-P and M-N. This roughly mirrors ELI, which had separate commands for matching in the history and cycling through the history.  See my earlier comments for why this is desirable: briefly, the key utility of the ELI style is the ability to build a new CL input line *around* a previously-entered input.

I do not believe that this is a final version, but it should provide an illustration of a productive direction.