Fix some syntax errors.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@63946 65c4cc65-6c06-0410-ace0-fbb531ad65f3

doc/qos.tex

@@ -8,7 +8,7 @@ congested with other traffic.
 Also asterisk running on Linux can set 802.1p CoS marks in VLAN packets 
 for all used VoIP protocols. It is useful when you are working in switched 
 enviropment. For maping skb->priority and VLAN CoS mark you need to use 
-command "vconfig set_egress_map [vlan-device] [skb-priority] [vlan-qos]".
+command "vconfig set\_egress\_map [vlan-device] [skb-priority] [vlan-qos]".
 
 \subsubsection{SIP}