Makefile.include: allow sending newline with cleanterm
Makefile.include: allow sending newline with cleanterm

Disable repeating the command on empty line to allow sending empty
lines.

yogo1212/RIOT,kaspar030/RIOT,x3ro/RIOT,jasonatran/RIOT,aeneby/RIOT,x3ro/RIOT,kYc0o/RIOT,OlegHahm/RIOT,toonst/RIOT,josephnoir/RIOT,miri64/RIOT,RIOT-OS/RIOT,toonst/RIOT,ant9000/RIOT,smlng/RIOT,kYc0o/RIOT,basilfx/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kaspar030/RIOT,josephnoir/RIOT,mtausig/RIOT,basilfx/RIOT,OTAkeys/RIOT,authmillenon/RIOT,yogo1212/RIOT,aeneby/RIOT,aeneby/RIOT,ant9000/RIOT,basilfx/RIOT,x3ro/RIOT,RIOT-OS/RIOT,x3ro/RIOT,miri64/RIOT,toonst/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,OlegHahm/RIOT,authmillenon/RIOT,x3ro/RIOT,basilfx/RIOT,authmillenon/RIOT,josephnoir/RIOT,ant9000/RIOT,mtausig/RIOT,aeneby/RIOT,aeneby/RIOT,smlng/RIOT,smlng/RIOT,OTAkeys/RIOT,jasonatran/RIOT,smlng/RIOT,miri64/RIOT,ant9000/RIOT,mtausig/RIOT,mtausig/RIOT,kaspar030/RIOT,yogo1212/RIOT,josephnoir/RIOT,kYc0o/RIOT,smlng/RIOT,miri64/RIOT,authmillenon/RIOT,kYc0o/RIOT,jasonatran/RIOT,jasonatran/RIOT,ant9000/RIOT,toonst/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,basilfx/RIOT,josephnoir/RIOT,OlegHahm/RIOT,authmillenon/RIOT,jasonatran/RIOT,miri64/RIOT,mtausig/RIOT,OTAkeys/RIOT,toonst/RIOT,kaspar030/RIOT,yogo1212/RIOT,kaspar030/RIOT,kYc0o/RIOT,yogo1212/RIOT