Checking in changes prior to tagging of version 0.53.

Changelog diff is:

diff --git a/Changes b/Changes
index 09883aa..3f95d09 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,7 @@
 Revision history for Perl extension CGI::Header.

+0.53 (1.00-RC6) May 19th, 2013
+
   [DOCUMENTATION]

     - update EXAMPLES