Request Review: 6902182: Starting with jdwp agent should not incur performance penalty

[Deneau, Tom]

Cross posting to hotspot-compiler-dev at openjdk.java.net and
serviceability-dev at openjdk.java.net since this review request touches
both compiler/runtime code and JVMTI code...

New webrev is at http://cr.openjdk.java.net/~tdeneau/6902182/webrev.05

This webrev addresses the comments made by Dan Daugherty in 
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2010-January/002450.html

This webrev includes the name change from
 jvmti_can_post_exceptions() to jvmti_can_post_on_exceptions()

New files that were not in previous webrevs:
   * jvmtiThreadState.hpp, 
        JvmtiEventControllerPrivate::recompute_thread_enabled() now calls a routine
        in here rather than in JavaThread directly

   * All other new files are due to the name change from
     jvmti_can_post_exceptions() to jvmti_can_post_on_exceptions()

-- Tom Deneau