Patch from Mark Lewis (wk42):

i've made a few adjustments to xtrn.cpp for external.bat...

- remove unneeded redirection of dosemu output.
   still uses same log file name and stops zero
   byte file dosemu.log from being created in node
   directories.
- fix faulty "keystroke" dosemu -I command. it
   didn't actually do the "\r" but sent it as
   characters to the command line.
- added code for SBBS specific lredirs to be
   done more cleanly like dosemu's default
   autoexec.bat. only deletes redir if it exists.

His editor also appears to have removed trailling white-space from this file,
which is fine.