bug.h: add include of it to various implicit C users

With bug.h currently living right in linux/kernel.h there
are files that use BUG_ON and friends but are not including
the header explicitly.  Fix them up so we can remove the
presence in kernel.h file.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/lib/timerqueue.c b/lib/timerqueue.c
index 191176a..14c6403 100644
--- a/lib/timerqueue.c
+++ b/lib/timerqueue.c
@@ -22,6 +22,7 @@
  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#include <linux/bug.h>
 #include <linux/timerqueue.h>
 #include <linux/rbtree.h>
 #include <linux/module.h>