Backported the fix to 5.1.
Problem: the auxiliary test files rpl_start_server.inc and rpl_stop_server.inc
write a file that is later read by mtr. The bug was that the file was written
with platform-dependent newline terminators, i.e., \r\n on windows, whereas mtr
only understands \n.
Fix: write the file so that it uses \n on all platforms.