[boost] Request for comments on changes to the dynamic_bitset docs

Hi, I just fixed the dynamic_bitset docs for issue #1591; the problem is with a couple of duplication of sentences of this kind: Note that the expression b1 & b2 is equivalent to creating a temporary copy of b1, using operator&=, and returning the temporary copy. I think such sentences are almost without meaning and should simply be dropped. The only concern is for "breaking a contract" in this case, though frankly I don't see what the user could sensibly rely upon. And "equivalent" is so generic, anyway. In case you agree with removing the sentences, would you note that in the section "Changes from previous version(s)"? -- Genny