RFR (XS): 8037043: put Method flag bits in predictable positions

[Christian Thalinger]

https://bugs.openjdk.java.net/browse/JDK-8037043
http://cr.openjdk.java.net/~twisti/8037043

8037043: put Method flag bits in predictable positions
Reviewed-by:

Currently Method flag bits are managed as a bit field which is C++ implementation specific. Sometimes we need to know the exact position of flag bits in its enclosing data type. For this reason other flag bits in HotSpot are implemented with enum shift values so the exact bit position can be easily identified.