update comment about BSON_STATIC
update comment about BSON_STATIC

bjori/libbson,ajdavis/libbson,mongodb/libbson,ajdavis/libbson,mapr/libbson,mapr/libbson,rcsanchez97/libbson,bjori/libbson,mongodb/libbson,rcsanchez97/libbson,ajdavis/libbson,rcsanchez97/libbson,mongodb/libbson,bjori/libbson,mapr/libbson