Deprecated std.c.*.socket and missing replacement

[Sebastiaan Koppe via Digitalmars-d-learn]

I am building a multicast application, and I am using the 
std.c.*.socket modules to provide the definition of the 
IP_ADD_MEMBERSHIP constant.

These modules are marked as deprecated telling me to look in 
core.sys.posix.* instead.

I grepped the complete sourcetree, but nowhere is the 
IP_ADD_MEMBERSHIP constant defined other than in the deprecated 
modules.

What to do?