Update RELEASE_CHANGES to mention updating the timezone database as

a routine part of release prep.

src/timezone/README

 This is a PostgreSQL adapted version of the timezone library
 from:
 
-	ftp://elsie.nci.nih.gov/pub/tz*.tar.gz
+	ftp://elsie.nci.nih.gov/pub/tzcode*.tar.gz
 
+The data files under data/ are an exact copy of the latest data set
+from
+
+	ftp://elsie.nci.nih.gov/pub/tzdata*.tar.gz
+
+Since time zone rules change frequently in some parts of the world,
+we should endeavor to update the data files before each PostgreSQL
+release.

src/tools/RELEASE_CHANGES

@@ -29,9 +29,11 @@
     update INSTALL
     platform-specific FAQ's, if needed
 
+* Update timezone data to match latest zic database (see src/timezone/README)
+
 * Update pg_upgrade to handle new version, or disable
 
-* Update copyright year?
+* Update copyright year when needed
 
 
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