Consistent header macros everywhere

src/common/thread.h

@@ -17,6 +17,9 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+#ifndef HEXCHAT_THREAD_H
+#define HEXCHAT_THREAD_H
+
 #if 0	/* native file dialogs */
 #include <windows.h>
 
@@ -29,3 +32,5 @@ typedef struct
 thread *thread_new (void);
 int thread_start (thread *th, void *(*start_routine)(void *), void *arg);
 #endif
+
+#endif