py/obj: Add support for __float__ and __complex__ functions.

tests/float/complex_dunder.py

@@ -0,0 +1,40 @@
+# test __complex__ function support
+
+
+class TestComplex:
+    def __complex__(self):
+        return 1j + 10
+
+
+class TestStrComplex:
+    def __complex__(self):
+        return "a"
+
+
+class TestNonComplex:
+    def __complex__(self):
+        return 6
+
+
+class Test:
+    pass
+
+
+print(complex(TestComplex()))
+
+try:
+    print(complex(TestStrComplex()))
+except TypeError:
+    print("TypeError")
+
+
+try:
+    print(complex(TestNonComplex()))
+except TypeError:
+    print("TypeError")
+
+
+try:
+    print(complex(Test()))
+except TypeError:
+    print("TypeError")