separate checks for 32- and 64-bit atomics
separate checks for 32- and 64-bit atomics

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