Fixed the #include in SpookyV2.cpp

SpookyV2.cpp was looking for SpookyV2.h vs
../../../boost/afio/detail/SpookyV2.h

I had gotten around that by just adding the include directory to the
jamfile, but this is probably better.

Optionally this could have been fixed by adding
<include>../../../boost/afio/detail to the project requirements in the
unit test jamfile