+ passfd: allow compilation on mingw
+ * modules/sys_socket (Depends-on): Add sys_uio.
+ * lib/sys_socket.in.h [!@HAVE_SYS_SOCKET_H@]: Use it for struct
+ iovec and a minimal struct msghdr.
+ * m4/afunix.m4 (gl_SOCKET_AFUNIX): Detect recvmsg/sendmsg.
+ * tests/test-sys_socket.c (main): Enhance test.
+ * lib/passfd.c (include): Drop <sys/uio.h>; <sys/sockets.h> is
+ guaranteed to provide what we need.
+ (sendmsg, recvmsg): Declare fallbacks if we lack sendmsg.
+ * modules/passfd-tests (Depends-on): Add sys_wait.
+ * tests/test-passfd.c (main): Skip test on mingw, for now.
+ * doc/posix-headers/sys_socket.texi (sys/socket.h): Document the
+ partial 'struct msghdr' implementation.
+