* src/threads/threads-common.c (threads_preinit): Create and

* src/threads/threads-common.c (threads_preinit): Create and
initialize the main-thread.
(threads_table_init): Changed signature, insert main-thread and
maintain a used list too.
(threads_table_add): Use locking and maintain used list.
(threads_table_remove): Likewise.
(threads_table_get): New function.
(threads_table_get_non_daemons): Likewise.
(threads_table_first): Likewise.
(threads_table_next): Likewise.
[!NDEBUG] (threads_table_dump): Use log_* functions.
(threads_dump): Use threads-table and functions.

* src/threads/threads-common.h (threads_table_entry_t): Made a struct
and renamed nextfree to next.
(threads_table_get): Added
(threads_table_get_non_daemons): Likewise.
(threads_table_first): Likewise.
(threads_table_next): Likewise.
[!NDEBUG] (threads_table_dump): Likewise.
(threads_impl_table_init): Likewise.
(threads_table_lock): Likewise.
(threads_table_unlock): Likewise.
(threads_set_current_threadobject): Likewise.

* src/threads/native/threads.c (threadlistlock): Removed.
(threads_impl_preinit): Removed main-thread initialization code.
(threads_impl_table_init): New function.
(threads_table_lock): New function.
(threads_table_unlock): Likewise.
(threads_init): Get main-thread from threads-table and removed
thread-list code.
(threads_attach_current_thread): Likewise.
(threads_detach_thread): Removed thread-list code.
(threads_find_non_daemon_thread): Removed.
(threads_join_all_threads): Use threads_table_get_non_daemons.