savevm.c: cleanup system includes

savevm.c suffers from the same problem as some other files.
Some years ago savevm.c was created from vl.c, moving some
code from there into a separate file.  At that time, all
includes were just copied from vl.c to savevm.c, without
checking which ones are needed and which are not.

But actually most of that stuff is _not_ needed.  More, some
stuff is wrong, for example, *BSD #ifdef'ery around <util.h>
vs <libutil.h> - for one, it fails to build on Debian/kFreebsd.

Just remove all this.  Maybe there's a possibility to clean
it up further - like removing <windows.h> (and maybe including
winsock.h for htons etc), and maybe it's possible to remove
some internal #includes too, but I didn't check this.

While at it, remove duplicate #include of qemu/timer.h.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
