Follow improvements in type signatures

testsuite/tests/ghc-regress/gadt/gadt-escape1.stderr

 
 gadt-escape1.hs:16:52:
     GADT pattern match with non-rigid result type `t'
-      Solution: add a type signature
+      Solution: add a type signature for the entire case expression
     In a case alternative: Hidden (ExpInt _) a -> a
     In the expression:
         case (hval :: Hidden) of { Hidden (ExpInt _) a -> a }

testsuite/tests/ghc-regress/gadt/gadt13.stderr

 
 gadt13.hs:12:5:
     GADT pattern match in non-rigid context for `I'
-      Solution: add a type signature
+      Probable solution: add a type signature for `shw'
     In the pattern: I t
     In the definition of `shw': shw (I t) = ("I " ++) . shows t

testsuite/tests/ghc-regress/gadt/gadt7.stderr

 
 gadt7.hs:12:31:
     GADT pattern match in non-rigid context for `K'
-      Solution: add a type signature
+      Probable solution: add a type signature for the scrutinee of the case expression
     In the pattern: K
     In a case alternative: K -> y1
     In the expression: case t1 of { K -> y1 }
 
 gadt7.hs:15:32:
     GADT pattern match in non-rigid context for `K'
-      Solution: add a type signature
+      Probable solution: add a type signature for the scrutinee of the case expression
     In the pattern: K
     In a case alternative: K -> y1
     In the expression: case t1 of { K -> y1 }

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail172.stderr

 
 tcfail172.hs:19:10:
     GADT pattern match in non-rigid context for `Nil'
-      Solution: add a type signature
+      Probable solution: add a type signature for `is_normal'
     In the pattern: Nil
     In the definition of `is_normal': is_normal Nil = True