Files returned by WriteToNewTempFile are cleaned up
automatically at the end of a test case execution.
WriteToNewTempFile now relies on the TB.TempDir()
function provided by the testing std package.
TempFile returns a temporary file that can be used
within a test case and is automatically removed
at the end of the test execution.
Prepare migrating testing auxiliary functions from tests
to testutil.
Remove local duplicates on testutil.WriteToNewTempFile().
Always favor testutil.NewTestCaseDir() over ioutil.TempDir().
Add test cases for the testing auxiliary functions.
Alessio Treglia