Modify {BRep,IGES,STEP}Import_test tests to check that changing locale has no impact

User has to select a non-C locale when configuring, otherwise these new checks are not performed.
Write files back onto disk to compare files written under C and non-C locales
Switch to C locale when reading IGES files

Inspired by a patch from http://tracker.dev.opencascade.org/view.php?id=22898
Switch to C locale when writing IGES files