tests/basics/string_compare.py: Add test with string that hashes to 0.

The string "Q+?" is special in that it hashes to zero with the djb2
algorithm (among other strings), and a zero hash should be incremented to a
hash of 1.

tests/basics/string_compare.py

@@ -53,3 +53,6 @@ print("1/" <= "1")
 # that does have a hash, but the lengths of the two strings are different
 import sys
 print(sys.version == 'a long string that has a hash')
+
+# this special string would have a hash of 0 but is incremented to 1
+print('Q+?' == 'Q' + '+?')