gnutls: Define EMSGSIZE on Windows systems
gnutls: Define EMSGSIZE on Windows systems

It isn’t clear whether all versions of MinGW define EMSGSIZE, so define
it to WSAEMSGSIZE as a fallback if it isn’t defined.

See:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms740668%28v=vs.85%29.aspx#wsaemsgsize

Based on a patch originally by Luciana Fujii
<luciana.fujii@collabora.com>.

https://bugzilla.gnome.org/show_bug.cgi?id=697908

GNOME/glib-networking,GNOME/glib-networking,GNOME/glib-networking