PEP 538: Fix title and add new post date

pep-0538.txt

@@ -1,5 +1,5 @@
 PEP: 538
-Title: Coercing the legacy C locale to C.UTF-8
+Title: Coercing the legacy C locale to a UTF-8 based locale
 Version: $Revision$
 Last-Modified: $Date$
 Author: Nick Coghlan <ncoghlan@gmail.com>
@@ -9,7 +9,8 @@ Content-Type: text/x-rst
 Created: 28-Dec-2016
 Python-Version: 3.7
 Post-History: 03-Jan-2017 (linux-sig),
-              07-Jan-2017 (python-ideas)
+              07-Jan-2017 (python-ideas),
+              05-Mar-2017 (python-dev)
 
 
 Abstract