Routine Name:	getsyndest

Description:	Returns a string which is the path of the postsynaptic
		element which receives the nth SPIKE message sent by the
		given presynaptic element.  Can also return the index of
		the synapse on this element.

Usage:		getsyndest presynaptic-element spikemsg-number -index

		presynaptic-element  The element sending SPIKE messages to
		        postsynaptic targets.

		spikemsg-number The number of the SPIKE message whose
			destination we want.  This can be obtained by getmsg
			or showmsg.

		-index This option returns the index of the synapse which
			receives the SPIKE message on the destination
			element.

Example:	str dest  = {getsyndest input[0]/spike 0}
		int index = {getsyndest input[0]/spike 0 -index}
		setfield {dest} synapse[{index}].weight 10.0

Notes:		getsynindex can also be used to get the index of a synapse
		if you know the names of the pre- and postsynaptic elements.

See also:	getsyncount, getsynindex, getsynsrc, BoG chapter 17

