Make str/str8 comparisons return True/False for !=/==.

Code that has been returning str8 becomes much more apparent thanks to this
(e.g., struct module returning str8 for all string-related formats or sqlite3
passing in str8 instances when converting objects that had a __conform__
method).  One also has to watch out in C code when making a key from char *
using PyString in the C code but a str instance in Python code as that will not
longer compare equal.

Once str8 gains a constructor like the current bytes type then
test_modulefinder needs a cleanup as the fix is a little messy in that file.

Thanks goes to Thomas Lee for writing the patch for the change giving an
initial run-down of why most of the tests were failing.
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index 0bdd036..d6a51dd 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -157,7 +157,7 @@
         s256 = "".join(["\n"] * 256 + ["spam"])
         co = compile(s256, 'fn', 'exec')
         self.assertEqual(co.co_firstlineno, 257)
-        self.assertEqual(co.co_lnotab, '')
+        self.assertEqual(co.co_lnotab, str8(''))
 
     def test_literals_with_leading_zeroes(self):
         for arg in ["077787", "0xj", "0x.", "0e",  "090000000000000",