RFR(XS): 8221306: JVMTI spec for FramePop(), MethodExit(), and MethodEnter() could use some cleanup

[serguei.spit...@oracle.com]

Please, review a fix for small spec bug:
  https://bugs.openjdk.java.net/browse/JDK-8221306

Webrev:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/jvmt-funcs-cleanup.1/src/

Updated JVM TI spec for the FramePop, MethodEntry and MethodExit events:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/jvmt-funcs-cleanup.1/docs/specs/jvmti.html#FramePop

Summary:
  It is a minor spec cleanup for JVM TI events FramePop/MethodEntry/MethodExit:
   - added small clarification that GetFrameLocation needs to be asked for frame at depth 0
   - removed partly unneeded and partly incorrect statements about MethodExit event argument

Testing:
  Manually verified the generated jvmti.html.

I think, there is no need to file a CSR for this spec update as it is just minor cleanup.

Thanks,
Serguei