The list of GDL routines to be executed during the make-check run is 
defined in the testsuite/LIST file. After adding a new item 
(filename) to the list, please rerun cmake.

Each test routine is invoked using the GDL "-e" command-line option.
CTests sets the status of a test based on the exit code of the script:
- "success" for exit code 0 
- "ignorable failure" for code 77
- "failure" for any other exit code, e.g. 1
Therefore, a failure of a GDL test should be indicated by e.g.:

  if ( ...true if test failed... ) begin
    message, 'reason for the failure', /continue
    exit, status=1
  endif

An ignorable failure can be indicated by e.g.:

  if (!XXX_exists()) then begin
    message, 'GDL was built w/o support for XXX - skipping', /conti
    exit, status=77
  endif

The name of the file must match the name of the test routine, e.g.
testsuite/test_dummy.pro for
  
  pro test_dummy
    ...
  end

GDL segfaults, assertion-exits, std::terminate() exits, etc. are 
handled as failures by CTest.
