Include qom/object.h and exec/memory.h instead of exec/ioport.h;
exec/ioport.h was almost everywhere required only for those two
includes, not for the content of the header itself.

Remove block/aio.h, everybody is already including it through
another path.

With this change, include/hw/hw.h is freed from qemu-common.h.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>