tests: Add some tests to improve coverage.

Used gcov to find some parts of vm.c, runtime.c, obj.c that were not
covered by any tests.  Still need to use gcov more thoroughly.

tests/basics/builtin_hash.py

@@ -1,5 +1,16 @@
 # test builtin hash function
 
+print(hash(False))
+print(hash(True))
+print({():1}) # hash tuple
+print({1 << 66:1}) # hash big int
+print(hash in {hash:1}) # hash function
+
+try:
+    hash([])
+except TypeError:
+    print("TypeError")
+
 class A:
     def __hash__(self):
         return 123