getpagesize on Linux returns an int. Fix QEMU's implementation for
Windows to return an int (instead of size_t), too.
This fixes a compiler warning which was introduced recently
(commit 093e3c42).
Backports commit a28c2f2df7679e3a87789e9fb7ed69331f697297 from qemu
qemu-common.h includes some fixups for things the Win32
headers don't define or define weirdly. These really
belong in os-win32.h, so move them there.
Backports commit 1aad8104f3b69206da1f868639e1f69c26f6d482 from qemu