tests/basics: Add tests for for-else statement.

tests/basics/for_else.py

+# test for-else statement
+
+# test optimised range with simple else
+for i in range(2):
+    print(i)
+else:
+    print('else')
+
+# test optimised range with break over else
+for i in range(2):
+    print(i)
+    break
+else:
+    print('else')
+
+# test nested optimised range with continue in the else
+for i in range(4):
+    print(i)
+    for j in range(4):
+        pass
+    else:
+        continue
+    break
+
+# test optimised range with non-constant end value
+N = 2
+for i in range(N):
+    print(i)
+else:
+    print('else')
+
+# test generic iterator with simple else
+for i in [0, 1]:
+    print(i)
+else:
+    print('else')
+
+# test generic iterator with break over else
+for i in [0, 1]:
+    print(i)
+    break
+else:
+    print('else')