bug#7343: Making flyspell incredibly fast when checking whole files

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Anyway, flyspell does try to take advantage of the above behavior by
> checking whether a region is larger than flyspell-large-region
> characters, and if so then it runs the spell checker as a separate
> process with "-l".  But then it does something that, in many cases, is
> rather ruinous: it takes every misspelling so identified, and passes it
> *back* through the normal interactive spell-checking logic!  This is
> because all of the real logic of what to do with a misspelling - how to
> highlight it, how to search for nearby instances of the same word, how
> to cache spellings, and so forth - is bound up in flyspell-word, so the
> flyspell-external-point-words function, which processes the actual
> misspellings discovered by flyspell-large-region, really has no other
> choice but to call flyspell-word for each misspelling.

IIUC this sounds very good (tho it only speeds up flyspell-region and
not flyspell-post-command-hook) and the patch looks good and small
enough for inclusion as a "tiny patch".  Agustin, could you double check
that it's OK and install it in the trunk if so?


        Stefan