skip-chars-forward v. re-search-forward

[Dave Love]

I've tended to use skip-chars-forward instead of re-search-forward
since it's byte-coded and I assumed it's more efficient.  However, I
made a measurement and found that skip-chars-forward was actually
slower than re-search-forward.

Is there a good reason for maintaining the two implementations?
Implementing skip-chars-forward using re-search-forward would have the
advantage that character classes would work with it, which they
currently don't.