This change should appease the mingw32 builds.
Similar to r293725.
LGTM, but please wait for dberris approval.
LG. std::errc::bad_message EBADMSG is used rarely, in STREAMS (which Linux chose not to implement; FreeBSD has very basic implementation) and very few network functions.
LGTM -- just FTR, since I missed this the first time around.