bug#15998: 24.3; forward-sexp (scan-sexps) doesn't do well with some SEXPs

[Shigeru Fukaya]

`forward-sexp', or `scan-sexps', doesn't seem to skip bool vectors correctly.

Bool vector's format is like #&N"XXX".
`forward-sexp' doesn't skip the whole bool vector, but stop before
double quotation.

And, maybe, just the same thing occurs for circular objects.
It skip only the label, and stop before the object.

Is the current behavior correct?

Regards,
Shigeru