Use diff --strip-trailing-cr in pg_regress.c

This was reverted in commit c194de0. However with a correct
collate.windows.win1252.out we can now re-enable it.

Discussion: https://postgr.es/m/CAN55FZ1objLz3Vn5Afu4ojNESMQpxjxKcp2q18yrKF4eKMLENg@mail.gmail.com

Author: adunstan