Fix space removing in modem ATD command

[NicknineTheEagle]

This snippet removing trailing spaces from ATD command line was not actually working.

[kcgen]

@NicknineTheEagle , can you show examples inside dosbox and/or a terminal program how this problematic code currently behaves versus how it should behave (perhaps with output from this PR)?

[NicknineTheEagle]

Easy to check, just open any terminal program type in "atdt bbs.dmine.net " (three trailing spaces). Right now, you'll get this:

SERIAL: Port 1 command sent to modem: ->ATDT BBS.DMINE.NET   <-
SERIAL: Port 1 connecting to host BBS.DMINE.NET    port 23.
SERIAL: Port 1 failed to connect.

With the fix, trailing spaces will get trimmed and the argument will get parsed properly:

SERIAL: Port 1 command sent to modem: ->ATDT BBS.DMINE.NET   <-
SERIAL: Port 1 connecting to host BBS.DMINE.NET port 23.
SERIAL: Port 1 modem response: CONNECT 57600.

[dreamer]

@NicknineTheEagle trimming this way is even better :)

Thank you!