Checking in changes prior to tagging of version 0.52.

Changelog diff is:

diff --git a/Changes b/Changes
index 3b82267..d9fc199 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,7 @@
 Revision history for Perl extension CGI::Header.

+0.52 (1.00-RC5) May 14th, 2013
+
   - Add tests for CGI::Header#clone. POD explains how CGI::Header copies
     its instances.
   - CGI::Header::Standalone#as_string removes CRLF from Status-Line properly.