quite messy implementation of generic lambdas, needs reworking; fixes #715

tests/generics/tgenericlambda.nim

@@ -0,0 +1,10 @@
+discard """
+  output: "10\n10"
+"""
+
+proc test(x: proc (a, b: int): int) =
+  echo x(5, 5)
+
+test(proc (a, b): auto = a + b)
+
+test do (a, b) -> auto: a + b

tests/generics/tmetafield.nim

@@ -1,7 +1,7 @@
 discard """
   cmd: "nimrod check $# $#"
   msg: "'proc' is not a concrete type"
-  msg: "'seq[Foo]' is not a concrete type."
+  msg: "'Foo' is not a concrete type."
   msg: "invalid type: 'TBaseMed'"
 """