RFR: 8153967: Remove top.hpp

[Stefan Karlsson]

Hi all,

Please review this patch remove the top.hpp file.

http://cr.openjdk.java.net/~stefank/8153967/webrev.01
https://bugs.openjdk.java.net/browse/JDK-8153967

It has been replaced by explicit includes and forward declarations, 
where needed. This is just a small step towards getting smaller include 
dependencies.

Tested with JPRT

Thanks,
StefanK