README: Add libperfstat as an optional dependency.

diff --git a/README b/README
index 14e11cf..2cb0a6f 100644 (file)
--- a/README
+++ b/README
@@ -570,6 +570,9 @@ Prerequisites
     Used to capture packets by the `dns' plugin.
     <http://www.tcpdump.org/>
 
+  * libperfstat (optional)
+    Used by various plugins to gather statistics under AIX.
+
   * libperl (optional)
     Obviously used by the `perl' plugin. The library has to be compiled with
     ithread support (introduced in Perl 5.6.0).