RFR(XS) 8140604: Internal Error runtime/stubRoutines.hpp:392 assert(_intrinsic_log != 0L) failed: must be defined

[Igor Veresov]

This is a little assert problem that was exposed by 8139575. The following change fixes the assert plus a little bit of cleanup.

Webrev: http://cr.openjdk.java.net/~iveresov/8140604/webrev.00/

Thanks,
igor