BasicType and BasicTypeSize should refer to HotSpot values

http://mail.openjdk.java.net/pipermail/serviceability-dev/2017-October/021965.html

Enum values in BasicType and BasicTypeSize are declared as const values. However, it makes error prone when existing enum values change.
They should refer to HotSpot values via VMStructs.

I attach suggested fix to this ticket.
This patch works fine on hotspot/jtreg/serviceability/sa jtreg tests.