Clear password when session ends

Any password stored in SCP_SESSION is now cleared before storage
is returned to the heap

sesman/libscp/libscp_session.c

@@ -427,14 +427,29 @@ scp_session_set_guid(struct SCP_SESSION *s, const struct guid *guid)
  return 0;
 }
 
+/*******************************************************************/
+static void
+clear_and_free_string(char *p)
+{
+ if (p != NULL)
+ {
+ char *cp;
+ for (cp = p ; *cp != '\0'; ++cp)
+ {
+ *cp = '\0';
+ }
+ g_free(p);
+ }
+}
+
 /*******************************************************************/
 void
 scp_session_destroy(struct SCP_SESSION *s)
 {
  if (s != NULL)
  {
  g_free(s->username);
- g_free(s->password);
+ clear_and_free_string(s->password);
  g_free(s->hostname);
  g_free(s->domain);
  g_free(s->program);