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/test-suite.sh

@@ -13,7 +13,7 @@ then
     AMOUNT=$(./regression_tests countall ../$FILE)
     RET=$?
     if [ $RET -ne 0 ]; then
-        echo ":test-result: SKIP: json is not enabled. (regression/$RET) ../$FILE:$i"
+        echo ":test-result: SKIP: json is not enabled. (regression/$RET) ../$FILE"
         exit 0
     fi
 
@@ -30,10 +30,10 @@ else
       RET=$?
       if [ $RET -eq 127 ]
       then
-          echo ":test-result: SKIP: json is not enabled. (unit/$RET) ../$FILE:$i"
+          echo ":test-result: SKIP: json is not enabled. (unit/$RET) ../$FILE"
       elif [ $RET -ne 0 ]
       then
-          echo ":test-result: FAIL possible segfault: (unit/$RET) ../$FILE:$i"
+          echo ":test-result: FAIL possible segfault: (unit/$RET) ../$FILE"
       fi
 fi