tests: Rename test scripts, changing - to _ for consistency.

From now on, all new tests must use underscore.

Addresses issue #727.

tests/basics/dict_intern.py

@@ -0,0 +1,15 @@
+# check that interned strings are compared against non-interned strings
+
+di = {"key1": "value"}
+
+# lookup interned string
+k = "key1"
+print(k in di)
+
+# lookup non-interned string
+k2 = "key" + "1"
+print(k == k2)
+print(k2 in di)
+
+# lookup non-interned string
+print("".join(['k', 'e', 'y', '1']) in di)