I needed to modify CreateScImportAsciiDlg signature so that we are able
to pass a pointer to a dialog parent window to ScImportAsciiDlg.

Moreover, I needed to perform the execution of the ScImportAsciiDlg
dialog in ScViewFunc::PasteDataFormat asynchronously, both for lok and
desktop case. In order to achieve this result it has been needed
to modify the lifespan of some objects previously local
to PasteDataFormat.

Since PasteDataFormat returns a boolean, I took care to check how this
return value is used. I found out 2 cases:
1) in ScViewFunc::PasteFromSystem where it is used for popping up an
error dialog box, informing the user in the case that the paste
operation is failed;
2) in ScGridWindow::ExecuteDrop where it is used for informing the
system window manager of the success or fail of the drag and drop
action.

The first case is now handled by a lamba invoked soon after the dialog
execution ended. The second case is more tricky: I handle it as
the paste operation is always successful, hoping it doesn't do any real
difference since the return value is used not by LO but by the system
window manager (e.g. gtk).

The asynchronous call and the behaviors described above occur only
when the paste operation involves some kind of simple text, in all other
cases nothing is changed.

Change-Id: Id4f96180a9336f665a22a2441ea490af993431b0
Reviewed-on: https://gerrit.libreoffice.org/53575Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>