RFR (S) [8u40] backport request 8065346 and 8064701

[Ioi Lam]

Hi,

Please review the backport of these two bugs from 9 to 8u40. The patches 
applied cleanly.

http://cr.openjdk.java.net/~iklam/8065346_8064701_backport_8u40/

8064701: Some CDS optimizations should be disabled if bootclasspath is 
modified by JVMTI
Summary: Added API to track bootclasspath modification

8065346: WB_AddToBootstrapClassLoaderSearch calls 
JvmtiEnv::create_a_jvmti when not in _thread_in_vm state
Summary: Removed ThreadToNativeFromVM and use 
java_lang_String::as_utf8_string instead

Thanks
- Ioi