Remove GDBSERVER uses from linux-btrace.c

This commit makes nat/linux-btrace.c include common-defs.h rather
than defs.h or server.h.  A couple of minor changes were required
to support this change.

gdb/ChangeLog:

	* nat/linux-btrace.c: Include common-defs.h.
	Don't include defs.h, server.h or gdbthread.h.
	* nat/linux-btrace.h (struct target_ops): New forward declaration.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2014-09-12  Gary Benson  <gbenson@redhat.com>
+
+	* nat/linux-btrace.c: Include common-defs.h.
+	Don't include defs.h, server.h or gdbthread.h.
+	* nat/linux-btrace.h (struct target_ops): New forward declaration.
+
 2014-09-12  Gary Benson  <gbenson@redhat.com>
 
 	* common/agent.c: Include common-defs.h.

gdb/nat/linux-btrace.c

@@ -19,15 +19,9 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-#ifdef GDBSERVER
-#include "server.h"
-#else
-#include "defs.h"
-#endif
-
+#include "common-defs.h"
 #include "linux-btrace.h"
 #include "common-regcache.h"
-#include "gdbthread.h"
 #include "gdb_wait.h"
 #include "x86-cpuid.h"
 

gdb/nat/linux-btrace.h

@@ -30,6 +30,8 @@
 #  include <linux/perf_event.h>
 #endif
 
+struct target_ops;
+
 /* Branch trace target information per thread.  */
 struct btrace_target_info
 {