* src/threads/native/threads.c, src/threads/native/threads.c: Further

* src/threads/native/threads.c, src/threads/native/threads.c: Further
cleanup. Still no functional changes.
Renamed external symbols are listed below.

* src/threads/native/critical.h, src/threads/native/critical.c: Cleanup.

* src/threads/native/lock.h: Cleanup.

* src/vm/jit/profile/profile.c (thread_sleep): Renamed to threads_sleep.

* src/vm/vm.c (joinAllThreads): Renamed to threads_join_all_threads.

* src/native/jni.c (thread_getself): Renamed to
threads_get_current_threadobject.

* src/native/vm/VMThread.c (thread): Typedef `thread` has been removed.
(interruptThread): Renamed to threads_interrupt_thread.
(isInterruptedThread): Renamed to threads_thread_has_been_interrupted.
(setPriorityThread): Renamed to threads_java_lang_Thread_set_priority.
(yieldThread): Renamed to threads_yield.
(interruptedThread): Renamed to threads_check_if_interrupted_and_reset.

* src/native/jvmti/cacaodbg.c (thread_getself): Renamed to
threads_get_current_threadobject.
(setthreadobject): Renamed to threads_set_current_threadobject.

* src/native/jvmti/jvmti.c (setthreadobject): Renamed to
threads_set_current_threadobject.

* src/threads/green/threads.h (yieldThread): Renamed to threads_yield.
(setPriorityThread): Renamed to threads_java_lang_Thread_set_priority.

* src/threads/green/threads.c (yieldThread): Renamed to threads_yield.
(setPriorityThread): Renamed to threads_java_lang_Thread_set_priority.