bson: initialize all fields and drop use of calloc().
bson: initialize all fields and drop use of calloc().

If we just initialize everything to the default, we can just use malloc
instead of calloc for a bit of a speed improvement.

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