RFC: Patch to implement WSARecvMsg and IP_PKTINFO

[Erich Hoover]

While searching for something else I discovered a bug relevant to the
interface-bound UDP broadcast patches I've been working on.
Apparently, IP_PKTINFO does work on Windows when used with the
WSARecvMsg function (Bug #19493).  I've attached a patch to address
this issue (including tests), and I would appreciate any comments on
it.  This patch approaches the problem by:
1) Implementing WSARecvMsg through WS2_recvfrom
2) Passing the control buffer as an additional WSABUF with an internal
flag (cleared internally to prevent confusing applications)
3) Converting the returned Unix IP_PKTINFO data to the equivalent
Windows version in WS2_recv() by utilizing a temporary buffer

Thanks in advance for your feedback.

Erich Hoover
[e-mail]