Request #30220:  Replace Textpad with Wordpad

To test this, remove your .mlworks_preferences if you have one, and
select the external editor from Usage->GeneralPreferences->Editor.
Then try to load an ML source file with a compilation error in it, and
the Error Browser should pop up.  Then select Edit->EditSource and
Wordpad should pop up displaying the ML source file.


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Request #30233:  Make platform specific editor dialogs.  Change Editor
interface.

The Win32 editor dialog (Usage->GeneralPreferences->Editor) now
contains three options.  One for directly specifying an editor
filename, another for specifying a single shot editor and the third
option for specifying an editor which communicates via a DDE link.
The single shot and DDE editors are chosen from a Combo box control.

On Motif, the editor dialog contains the above options but the DDE 
editor is changed to be a socket based editor, but works in a similar
(two-way) way.  Also, on Motif, the user specifies the single shot
editor and the socket based editor using a single selection list box.
There is now no separate way to specify emacs as the editor except
through choosing it from the list of socket-based editors, ie. the
emacs server option has been removed.

The Shell.Options.Preferences structure is now changed to reflect this
in that the customEditorName is replaced by two options - a
oneWayEditorName and a twoWayEditorName (single shot and
DDE/socket-based editor names respectively).  The Shell.Editor.Custom
structure has also changed to include the following functions:
commandNames() : returns a list of one way editors.
dialogNames() : returns a list of two way editors.
removeCommand : removes a one way editor from the list.
removeDialog : removes a two way editor from the list.
These structure changes can be easily inspected from the System
Browser.


