Configure test fixture using CTest for Windows build

- Added new test/test_suite.in with list of regression and unit tests
  previously in Makefile.am, to be shared between Unix and Windows
  builds.
- Updated regression.cc & unit.cc to return the number of failed tests
  to indicate to CTest that the test failed. Similarly, a crash or
  unhandled exception terminates the process with a non-zero exit code.
  - This change doesn't affect running the tests with autotest in Unix
    builds because this processes test output from custom-test-driver &
    test-suite.sh, and ignores the exit code of the test runner.
- Removed comment in test/test-cases/regression-offset-variable.json as
  this is not supported by JSON and prevents strict parsers to read and
  process the file.
- Minor change in regression.cc's clearAuditLog to replace std::ifstream
  with std::ofstream as the mode to open the flag applies to an output
  stream.
- Minor change in unit.cc to simplify code that deletes tests.
- Minor changes to test/custom-test-driver to correct usage information.

test/custom-test-driver

@@ -42,9 +42,9 @@ print_usage ()
 {
   cat <<END
 Usage:
-  test-driver --test-name=NAME --log-file=PATH --trs-file=PATH
-              [--expect-failure={yes|no}] [--color-tests={yes|no}]
-              [--enable-hard-errors={yes|no}] [--]
+  test-driver --test-name NAME --log-file PATH --trs-file PATH
+              [--expect-failure {yes|no}] [--color-tests {yes|no}]
+              [--enable-hard-errors {yes|no}] [--]
               TEST-SCRIPT [TEST-SCRIPT-ARGUMENTS]
 The '--test-name', '--log-file' and '--trs-file' options are mandatory.
 END