Update docs to point to the timezone library's new home at IANA.

The recent unpleasantness with copyrights has accelerated a move that
was already in planning.

src/timezone/README

@@ -1,12 +1,18 @@
-This is a PostgreSQL adapted version of the timezone library
-from:
+src/timezone/README
 
-	ftp://elsie.nci.nih.gov/pub/tzcode*.tar.gz
+Timezone
+========
 
-The data files under data/ are an exact copy of the latest data set
-from
+This is a PostgreSQL adapted version of the timezone library from
+http://www.iana.org/time-zones
 
-	ftp://elsie.nci.nih.gov/pub/tzdata*.tar.gz
+The source code can be found at:
+
+	ftp://ftp.iana.org/tz/releases/tzcode*.tar.gz
+
+The data files under data/ are an exact copy of the latest data set from:
+
+	ftp://ftp.iana.org/tz/releases/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