The system uses ssize_t so it can return -1 in case of an error. But in
our case, we will transform that to an AK::Error, thus we never return
-1. Let's return size_t instead.
SocketAddressWindows.h contains a bunch of copy-pasted Windows
definitions. This started causing ad-nauseam redefinition errors when
implementing the HTTP disk cache for Windows.
Instead, let's forward-declare the types we can in SocketAddress.h and
only define the couple of constants that we need. We can then assert at
compile-time that we defined them correctly.
