bashrc: define SSH_AUTH_SOCK before using

bashrc

@@ -10,6 +10,8 @@ if [ -e /bin/cygwin1.dll ]; then
     # cygwin ssh-agent support, from
     # http://www.webweavertech.com/ovidiu/weblog/archives/000326.html
 
+    export SSH_AUTH_SOCK=/tmp/.ssh_socket
+
     ssh-add -l 2>&1 >/dev/null
 
     if [ $? = 2 ]; then