made tests green again

tests/reject/tenummix.nim

@@ -1,6 +1,6 @@
 discard """
   file: "system.nim"
-  line: 643
+  line: 646
   errormsg: "type mismatch"
 """
 

tests/run/mmultim3.nim

@@ -1,5 +1,5 @@
 type
-    TObj* = object
+    TObj* = object {.inheritable.}
 
 var myObj* : ref TObj
 

tests/run/tmultim1.nim

@@ -5,7 +5,7 @@ discard """
 # Test multi methods
 
 type
-  Expression = ref object
+  Expression = ref object {.inheritable.}
   Literal = ref object of Expression
     x: int
   PlusExpr = ref object of Expression

tests/run/tmultim2.nim

@@ -5,7 +5,7 @@ discard """
 # Test multi methods
 
 type
-  TThing = object
+  TThing = object {.inheritable.}
   TUnit = object of TThing
     x: int
   TParticle = object of TThing

tests/run/tofopr.nim

@@ -5,7 +5,7 @@ discard """
 # Test is operator
 
 type
-  TMyType = object
+  TMyType = object {.inheritable.}
     len: int
     data: string