find_sources - how to access sources of CARL programs

The command
	
	% help sources

lists all the CARL programs for which sources can be found by the help program. 

To locate the source for a particular program, for instance, comb, say

	% help sources/comb

which prints the complete path to the program.

For the savants who are into clever hacks (and who are using the cshell) 
it is possible to say

	% vi `help sources/comb`

and have the vi editor started up on the file that help identifies
as the source.

The sources database covers all programs currently distributed by CARL.
Only programs are listed, not subroutines.  The root
directories for the various CARL libraries are mentioned as well.
