bugfix: better implict 'items' support

tests/compile/titerovl.nim

@@ -0,0 +1,21 @@
+discard """
+  output: '''9
+1
+2
+3
+'''
+"""
+
+# Test the new overloading rules for iterators:
+
+# test that iterator 'p' is preferred:
+proc p(): seq[int] = @[1, 2, 3]
+iterator p(): int = yield 9
+
+for x in p(): echo x
+
+# test that 'q' works in this position:
+proc q(): seq[int] = @[1, 2, 3]
+
+for x in q(): echo x
+