The allocator in malloc-pc has been extracted, so it can be used in every arch.
This operation showed that both the alloc and free functions can be also
generic.
Because of this, the QGuestAllocator has been removed from is function to wrap
the alloc and free function, and now just contains the allocator parameters.
As a result, only the allocator initalizer and unitializer are arch dependent.

Signed-off-by: Marc Marí <marc.mari.barcelo@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>