RFR: 8068349: Removed unused fast_iagetfield() function.

[Max Ockner]

Hello all,
please review yet another code removal. This is the Open portion of the fix:

Bug: https://bugs.openjdk.java.net/browse/JDK-8068349
Webrev: http://cr.openjdk.java.net/~mockner/8068349/

Summary: The function fast_iagetfield() is never used, and has been removed.

Tested with jtreg runtime tests.

Thanks,
Max Ockner