MINOR: global: add option to disable numa detection

Render numa detection optional with a global configuration statement
'no numa-cpu-mapping'. This can be used if the applied affinity of the
algorithm is not optimal. Also complete the documentation with this new
keyword.

doc/configuration.txt

@@ -919,6 +919,7 @@ The following keywords are supported in the "global" section :
    - nbproc
    - nbthread
    - node
+   - numa-cpu-mapping
    - pidfile
    - pp2-never-send-local
    - presetenv
@@ -1540,6 +1541,17 @@ nbthread <number>
   like "taskset" or "cpuset". Otherwise, this value defaults to 1. The default
   value is reported in the output of "haproxy -vv". See also "nbproc".
 
+numa-cpu-mapping
+  By default, if running on Linux, haproxy inspects on startup the CPU topology
+  of the machine. If a multi-socket machine is detected, the affinity is
+  automatically calculated to run on the CPUs of a single node. This is done in
+  order to not suffer from the performance penalties caused by the inter-socket
+  bus latency. However, if the applied binding is non optimal on a particular
+  architecture, it can be disabled with the statement 'no numa-cpu-mapping'.
+  This automatic binding is also not applied if a nbthread statement is present
+  in the configuration, or the affinity of the process is already specified,
+  for example via the 'cpu-map' directive or the taskset utility.
+
 pidfile <pidfile>
   Writes PIDs of all daemons into file <pidfile> when daemon mode or writes PID
   of master process into file <pidfile> when master-worker mode. This option is