[vectorIntrinsics] RFR: Some cleanups in Java code

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/panama/vector/cleanup.01/webrev.00/

Some minor cleanups:
   - remove unused opcodes
   - remove redundant default implementations
   - sprinkle additional @ForceInline annotations

Testing: jdk/incubator/vector tests

Best regards,
Vladimir Ivanov