[9] RFR (M): 8050052: Small cleanups in java.lang.invoke code

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/8050052/webrev.00
https://bugs.openjdk.java.net/browse/JDK-8050052

Numerous small code cleanups in java.lang.invoke package.

Testing: jtreg, nashorn, octane w/ "-ea -esa" and COMPILE_THRESHOLD={0,30}.

Reviewed-by: vlivanov, ?
Contributed-by: john.r.rose at oracle.com

Thanks!

Best regards,
Vladimir Ivanov