All JVMTI events have been changed to pass jvmtiEnv* and in most cases JNIEnv*.
The new agent thread start callback needs these too.

The JVMTI environment is critical information in a multiple agent situation.
The JNI environment is needed to perform JNI operations.

Lack of the JNI parameter in the analogous JVMDI callback has been a
maintenance issue for some time. This is the opertunity to address
this problem at its source. See bugs 4432884 and 4657650.