Building with HP's cc on HP-UX turned up a couple of problems.
_PyGILState_NoteThreadState was declared as static inconsistently.
Make it static as it's not necessary outside of this module.

Some tests failed because errno was reset to 0. (I think the tests
that failed were at least: test_fcntl and test_mailbox).
Ensure that errno doesn't change after a call to Py_END_ALLOW_THREADS.
This only affected debug builds.

This needs to be ported to HEAD.  I'll try to remember to do that tomorrow.
(Anyone, feel free to port it.)
diff --git a/Misc/NEWS b/Misc/NEWS
index 1feda61..fe9532a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -19,6 +19,9 @@
 Core and builtins
 -----------------
 
+- Make _PyGILState_NoteThreadState() static, it was not used anywhere
+  outside of pystate.c and should not be necessary.
+
 - Bug #1551432: Exceptions do not define an explicit __unicode__ method.  This
   allows calling unicode() on exceptions classes directly to succeed.