[MEDIUM] session: make session_shutdown() an independant function

We already had the ability to kill a connection, but it was only
for the checks. Now we can do this for any session, and for this we
add a specific flag "K" to the logs.
diff --git a/src/log.c b/src/log.c
index d750349..b62eeda 100644
--- a/src/log.c
+++ b/src/log.c
@@ -52,7 +52,7 @@
 	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
 };
 
-const char sess_term_cond[9]  = "-cCsSPRID";	/* normal, CliTo, CliErr, SrvTo, SrvErr, PxErr, Resource, Internal, Down */
+const char sess_term_cond[10] = "-cCsSPRIDK";	/* normal, CliTo, CliErr, SrvTo, SrvErr, PxErr, Resource, Internal, Down, Killed */
 const char sess_fin_state[8]  = "-RCHDLQT";	/* cliRequest, srvConnect, srvHeader, Data, Last, Queue, Tarpit */
 
 /*