pdk_runners
	This declares test runners for various file types.  By default,
	the shell_runner expects files to be named test_*.sh or test_*.csh
	because it is too easy to accidentally pick up a script otherwise.
	But, if you declare a file to be a test in pdk_runners, you don't
	have to have test_ in the name of the test.

simple.sh
	a simple test: does expr know that 1 + 1 = 2 ?  This includes
	some error reporting, e.g. if expr is not found

very_simple.sh
	an extraordinarily simple test written in sh.

sh_ref.sh
	/bin/sh example that compares output files. This uses functions
	defined by pandokia.

csh_ref.csh
	/bin/csh example that compares output files.  csh does not have
	functions and all the work-arounds are pretty hacky.  This example
	is exactly the same as sh_ref.sh except that all the work is
	written into the test intead of into a library.

