docs: add docs for bson_iter_timestamp(3).
docs: add docs for bson_iter_timestamp(3).

bjori/libbson,paulmelnikow/libbson,derickr/libbson,alexeyvo/libbson,bjori/libbson,jqk6/libbson,Convey-Compliance/libbson,derickr/libbson,mongodbinc-interns/libbson,ksuarz/libbson,ajdavis/libbson,paulmelnikow/libbson,ajdavis/libbson,Convey-Compliance/libbson,ksuarz/libbson,derickr/libbson,Machyne/libbson,jqk6/libbson,paulmelnikow/libbson,derickr/libbson,ajdavis/libbson,4Second2None/libbson_tmp,mapr/libbson,alexeyvo/libbson,paulmelnikow/libbson,remicollet/libbson,paulmelnikow/libbson,ksuarz/libbson,4Second2None/libbson_tmp,Machyne/libbson,rcsanchez97/libbson,jqk6/libbson,rayyang2000/libbson,remicollet/libbson,mapr/libbson,Machyne/libbson,Machyne/libbson,remicollet/libbson,mapr/libbson,rayyang2000/libbson,Convey-Compliance/libbson,jqk6/libbson,rayyang2000/libbson,alexeyvo/libbson,mongodb/libbson,rcsanchez97/libbson,mongodbinc-interns/libbson,remicollet/libbson,4Second2None/libbson_tmp,mongodbinc-interns/libbson,mongodb/libbson,rcsanchez97/libbson,mongodb/libbson,rayyang2000/libbson,bjori/libbson,4Second2None/libbson_tmp,mongodbinc-interns/libbson