*: Port Christians tweaks for 32-bit route tags

Port over Christian's tweaks from his port of my commit widening the
route-tag field width to 32-bit.  Commit dc9ffce8786844
 "*: Consistently support 32-bit route tags".

with "changes which make this actually useful for all the daemons".

This is missing the zebra route-map changes.
diff --git a/lib/zclient.c b/lib/zclient.c
index eb8de1a..a32faaa 100644
--- a/lib/zclient.c
+++ b/lib/zclient.c
@@ -530,7 +530,7 @@
   * If ZAPI_MESSAGE_METRIC is set, the metric value is written as an 8
   * byte value.
   *
-  * If ZAPI_MESSAGE_TAG is set, the tag value is written as a 2 byte value
+  * If ZAPI_MESSAGE_TAG is set, the tag value is written as a 4 byte value
   *
   * XXX: No attention paid to alignment.
   */