8165315: [ppc] Port "8133749: NMT detail stack trace cleanup"
Summary: Also add methods to check for slow/fastdebug to Platform.java.
Reviewed-by: simonis, cjplummer, dholmes
8164086: Checked JNI pending exception check should be cleared when returning to Java frame
Summary: Transitions to Java clear the pending pointer
Reviewed-by: dholmes, neliasso, coleenp