DOC: remove last occurrences of "HA-Proxy" syntax

There were only a few more used as output examples and comments in a few
docs, it was the right moment to get rid of them. The file intro.txt
which explains how to parse the version also got a hint about the possible
presence of a hyphen in the name in older versions.
diff --git a/doc/management.txt b/doc/management.txt
index 75e872b..fd96272 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -358,7 +358,7 @@
 you will systematically be asked for when posting a bug report :
 
   $ haproxy -vv
-  HA-Proxy version 1.6-dev7-a088d3-4 2015/10/08
+  HAProxy version 1.6-dev7-a088d3-4 2015/10/08
   Copyright 2000-2015 Willy Tarreau <willy@haproxy.org>
 
   Build options :