ObjFW  Check-in [4e59d2692f]

LLP64 was mostly fast enumeration using an unsigned long for the state,
which can't store a pointer or a size_t on LLP64. This is now solved by
either throwing an OFOutOfRangeException if the value of the size_t is
bigger than ULONG_MAX or storing the pointer in the extra field (copied
using memcpy, as it's an array of unsigned long, which again would be
too small to store a pointer).

Win64 was mostly Microsoft not being able to decide whether a length is
a size_t, a DWORD, an int or an unsigned int (thus the different types
in places that seem to be almost the same). But since that would not be
confusing enough, a file descriptor is an int if it's for a file, but a
long long if it is for a socket. But of course, for ReadFile and friends
it's a DWORD instead of an int then.