Add forgotten documentation for new channel variables added in 214309.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@214355 65c4cc65-6c06-0410-ace0-fbb531ad65f3

doc/tex/channelvariables.tex

@@ -793,6 +793,9 @@ ${TIMESTAMP}           * Current date time in the format: YYYYMMDD-HHMMSS
                          (Deprecated; use ${STRFTIME(${EPOCH},,%Y%m%d-%H%M%S)})
 ${TRANSFER_CONTEXT}      Context for transferred calls
 ${FORWARD_CONTEXT}       Context for forwarded calls
+${DYNAMIC_PEERNAME}      The name of the channel on the other side when a dynamic
+                         feature is used.
+${DYNAMIC_FEATURENAME}   The name of the last triggered dynamic feature.
 ${UNIQUEID}            * Current call unique identifier
 ${SYSTEMNAME}          * value of the systemname option of asterisk.conf
 ${ENTITYID}            * Global Entity ID set automatically, or from asterisk.conf