[experimental-ims] c67397f Add note about thread_pool_max

[Geoff Simmons]

commit c67397fa3ff06faeec7dd0322c07f28187bb30c6
Author: Andreas Plesner Jacobsen <apj at mutt.dk>
Date:   Tue Aug 16 16:22:10 2011 +0200

    Add note about thread_pool_max

diff --git a/doc/sphinx/installation/upgrade.rst b/doc/sphinx/installation/upgrade.rst
index 5f40422..ee57df4 100644
--- a/doc/sphinx/installation/upgrade.rst
+++ b/doc/sphinx/installation/upgrade.rst
@@ -112,3 +112,5 @@ Changes to behaviour
 ====================
 
 Varnish will return an error when headers are too large instead of just ignoring them. If the limits are too low, Varnish will return HTTP 413. You can change the limits by increasing http_req_hdr_len and http_req_size.
+
+thread_pool_max is now per thread pool, while it was a total across all pools in 2.1. If you had this set in 2.1, you should adjust it for 3.0.