Add wrapper for strtoull() function. Include unit tests.
Signed-off-by: Carlos L. Torres <carlos.torres@rackspace.com>
Message-Id: <e0f0f611c9a81f3c29f451d0b17d755dfab1e90a.1437346779.git.carlos.torres@rackspace.com>
[Use uint64_t in prototype. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>