extend looking-at's doc to point to looking-at-p

[Peter Tury]

Hi,

(I am not sure if I should post this request here; please advise if
there is a better place)

I suggest to modify the end of the doc of `looking-at' to refer to
`looking-at-p'. Something like this might be OK:

"This function modifies the match data that `match-beginning',
`match-end' and `match-data' access; if you want to preserve their
original content, then use `looking-at-p' instead; or save and restore
the match data..."

Thanks,P