Send updated manuscript before referees' response Is it common to send an updated manuscript to a publisher before the initial referees' report, if you have fixed a number of typos and ambiguities in the meantime?

EDIT: By fixing ambiguities, I mean for example writing down definitions that were previously just implied, or adding short examples every here and there.
That is, I think the changes I made are likely to help the referee understanding the manuscript.
The manuscript is on a mathematical subject.
There is nothing you can typically do during review -- the reviewers have received their copy of the manuscript that they were asked to review, and as an editor I would leave it at that even if I got an updated version. My response (in different words) to the author would have been "Well, these are things you should have thought about before submitting the paper."

But assuming the first version wasn't terrible, you will get the opportunity to roll your changes into any revisions you make in response to the reviewer comments.