dot/inputrc: Miscellaneous tweaks I didn't know about before.

dot/inputrc: Miscellaneous tweaks I didn't know about before.

  * Don't ding the bell for completion or cursor movement out-of-bounds.

  * Highlight completed filenames using the prevailing ls(1)
    colours.  (But continue not highlighting the existing prefix.)

  * Do the bracketed-paste thing to make mis-aimed pastes less
    dangerous.  (This may also cause some annoyance, but I think I'm
    willing to tolerate that for the extra safety.)

  * Use Readline macros to bind M-SPC to a simulacrum of `just-one-
    space'.  The documentation of Readline macros is rather unclear
    about which level the macro characters are inserted.  It turns out
    that they're keyboard macros.