* jvmti.cc (_envListLock): Change type to
        ReentrantReadWriteLock.
        (_Jv_JVMTI_DisposeEnvironment): Switch to read/write
        lock.
        (check_enabled_event): Likewise.
        (_Jv_GetJVMTIEnv): Likewise.
        (_Jv_JVMTI_Init): Likewise.
        (_Jv_JVMTI_PostEvent): Likewise.

From-SVN: r121616