Add checks for programs which are required for the test suite to run.
All prerequisite programs are checked for existance, and if any are
missing,
a list of missing programs is printed, and the test suite is aborted.
All programs currently used in the tests, except those in core-utils,
are checked.
requesting all changes
abort: error: Connection refused
255
ls: copy: No such file or directory
requesting all changes
abort: HTTP Error 404: File not found
255