Confirmed from HB9HBY's log: ptt=true, yet the FT-891 dropped to RX between
words during a CQ macro — while the same SCU-17 works in N1MM. Root cause:
go.bug.st/serial drives DTR/RTS through GetCommState/SetCommState, which on the
SCU-17's Silicon Labs CP210x drops the asserted RTS (PTT) the moment DTR (CW)
is toggled. N1MM/WSJT use EscapeCommFunction, which sets one line without
disturbing the other.
OpsLog now drives the lines the same way: a new lineCtl abstraction with a
Windows implementation (linectl_windows.go) that opens the COM port via
CreateFile and toggles DTR/RTS with windows.EscapeCommFunction (SETDTR/CLRDTR/
SETRTS/CLRRTS). linectl_other.go keeps go.bug.st/serial for non-Windows builds.
The serial keyer holds a lineCtl instead of a serial.Port. RTS (PTT) now stays
asserted for the whole macro, so the rig holds TX between words.
Promotes golang.org/x/sys to a direct dependency.
