fdo#60338: Introduce osl_createDirectoryWithFlags

...so that utl::TempFile can pass osl_File_OpenFlag_Private and doesn't have to
resort to umask (the calls to umask around Directory::create had somewhat
erroneously been removed recently with 1d72a0262c4570631d0aa8f98e34e21fb9d6ae42
"Related fdo#60338: Create missing temp file dir with user's original umask,"
mistaking this for creation of intermediate directories in the hierarchy).

On Windows, the flags argument to osl_createDirectoryWithFlags is ignored
completely for now.

Change-Id: Iac56a5049d579be729a3f338aa62105123edb6cb