bug#1299: lispref - searching.texi: Updating of looking-back arguments and return values in the example

[martin rudalics]

> See the diff attached. Note that I copied the explanation for greedy
> argument of `looking-back' function. Because I'm not a native speaker
> so probably this paragraph requires some rephrasing.

FWIW, it might not harm to also resolve the contradiction that REGEXP
can match _before_ LIMIT when GREEDY is non-nil (in the manual _and_ the
doc-string).

martin