Revisit -no-console option for Windows

The reason for ShowWindow opose to your FreeConsole is because if you start up
cmd.exe and do syncthing.exe -no-output it actually hides the existing cmd.exe
window oppose to opening a separate window and then hiding it, which keeps the
existing console hanging on syncthing.exe running.

I tried playing around with compiling as GUI, then given the option is not present
allocating a console, and redirecting the std streams to the new console, but that
seems ugly as I'd have to make quite a few calls. But that does get of the initial
flash.

internal/osutil/hidden_unix.go

@@ -24,3 +24,5 @@ func HideFile(path string) error {
 func ShowFile(path string) error {
 	return nil
 }
+
+func HideConsole() {}