Add 6.10 output for tests gadt11, tcfail155, tcfail176

testsuite/tests/ghc-regress/gadt/gadt11.stderr-6.10

+
+gadt11.hs:9:2:
+    Data constructor `B1' returns type `X' instead of its parent type
+    In the definition of data constructor `B1'
+    In the data type declaration for `B'

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail155.stderr-6.10

+
+tcfail155.hs:8:5:
+    Data constructor `P' returns type `L2' instead of its parent type
+    In the definition of data constructor `P'
+    In the data type declaration for `T'

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail176.stderr-6.10

+
+tcfail176.hs:7:20:
+    Data constructor `Bug' returns type `Maybe'
+      instead of its parent type
+    In the definition of data constructor `Bug'
+    In the newtype declaration for `Bug'