Add -vet-extra (checks for unneeded casts and transmutes)

src/llvm_backend.hpp

@@ -61,9 +61,6 @@ struct lbAddr {
 			Type *type;
 			Type *result;
 		} map;
-		struct {
-			i32 value_index;
-		} bit_field;
 		struct {
 			Selection sel;
 		} ctx;