#22 File drag to new session or hotlist edit

[Darren Salt]

This patch allows the dragging of files to the new
session window and the hotlist entry editing window.

Dragging URL and URI files causes the URL, if it's of
a supported scheme, to be inserted into the host icon.
The session type is modified appropriately, though
only telnet and ansitaskwindow are currently
recognised.

Dragging another file type will, if it's in the
runnables list, cause its name to be inserted into the
command icon. The session type is set to ANSI task.

The low-level routines for adding to and removing
from the runnables list are implemented; the list is
saved to and read from the choices file. The default
is &FF8 only.

[Darren Salt]

Patch to allow URL/filename insertion in new session & hotlist entry edit windows