RFR (XS): 8141677: Improve java.lang.invoke.MemberName hashCode implementation

[Claes Redestad]

Hi,

MemberName::hashCode is exercised during startup of jake, and is 
currently implemented using Objects.hash(...), which allocates Object[]s 
and boxes bytes.

Inlining this makes this slightly more efficient before the JIT kicks 
in, but more measurably allows initialization of Byte$ByteCache to be 
deferred from startup:

bug: https://bugs.openjdk.java.net/browse/JDK-8141677
webrev: http://cr.openjdk.java.net/~redestad/8141677/webrev.01/

/Claes