bsd-user: pull in target_arch_thread.h update target_arch_elf.h

Update target_arch_elf.h to remove thread_init. Move its contents to
target_arch_thread.h and rename to target_thread_init(). Update
elfload.c to call it. Create thread_os_thread.h to hold the os specific
parts of the thread and threat manipulation routines. Currently, it just
includes target_arch_thread.h. target_arch_thread.h contains the at the
moment unused target_thread_set_upcall which will be used in the future
when creating actual thread (i386 has this stubbed, but other
architectures in the bsd-user tree have real ones). FreeBSD doesn't do
AT_HWCAP, so remove that code. Linux does, and this code came from there.

These changes are all interrelated and could be brokend down, but seem
to represent a reviewable changeset since most of the change is boiler
plate.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Kyle Evans <kevans@FreeBSD.org>

bsd-user/netbsd/target_os_thread.h

@@ -0,0 +1,25 @@
+/*
+ *  NetBSD thread dependent code and definitions
+ *
+ *  Copyright (c) 2013 Stacey D. Son
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TARGET_OS_THREAD_H_
+#define _TARGET_OS_THREAD_H_
+
+#include "target_arch_thread.h"
+
+#endif /* !_TARGET_OS_THREAD_H_ */