fold verify_iovec() into copy_msghdr_from_user()

... and do the same on the compat side of things.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc include/linux/socket.h
Simple merge

diff --cc include/net/compat.h
Simple merge

diff --cc net/compat.c
Simple merge

diff --cc net/core/iovec.c
Simple merge

diff --cc net/socket.c
Simple merge