new tester; all tests categorized

tests/iter/titer4.nim

@@ -0,0 +1,10 @@
+discard """
+  file: "titer4.nim"
+  line: 7
+  errormsg: "iterator within for loop context expected"
+"""
+# implicit items/pairs, but not if we have 3 for loop vars:
+for x, y, z in {'a'..'z'}: #ERROR_MSG iterator within for loop context expected
+  nil
+
+