(svn r17001) -Codechange: replace some more assert(0)s to NOT_REACHED() and document why they (assert(0)) have to stay for the remaining cases.

src/yapf/yapf_base.hpp

@@ -275,9 +275,7 @@ public:
 				 *  - PfCalcEstimate() gives too large numbers
 				 *  - PfCalcCost() gives too small numbers
 				 *  - You have used negative cost penalty in some cases (cost bonus) */
-				assert(0);
-
-				return;
+				NOT_REACHED();
 			}
 			return;
 		}