build: check for Glibc 2.19 to handle _BSD_SOURCE vs _GNU_SOURCE
build: check for Glibc 2.19 to handle _BSD_SOURCE vs _GNU_SOURCE

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