bug#6227: Color isearch regexp submatches differently

[Juri Linkov]

>> but set I suggest a default of 100. The loop costs essentially nothing
>> for non-submatches and this is on command level.
>
> (/ (length (match-data)) 2)

Then the loop should iterate from 1 up to the minimum of
`(/ (length (match-data)) 2)' and `search-highlight-submatches'.

As for the faces, perhaps we should dynamically create submatch faces
like in `vc-annotate-lines' that uses `vc-annotate-color-map'.

-- 
Juri Linkov
http://www.jurta.org/emacs/