[Linux] added basic support for "notify" command

[GWRon]

This should work an many distributions. Without "notify" just does nothing except printing the text to the standard console (not visible in all cases).

[GWRon]

Someone should decide if this PR is worth to get merged or not.

[GWRon]

Bump.

[GWRon]

@woollybah
Maybe we should fall back to "print" if xmessage is not installed?

[GWRon]

For NG we would of course need to do the same in "brl.mod/systemdefault.mod"

[woollybah]

Presumably xmessage may not be installed?

[GWRon]

It's like saying x11 is not installed but relaying on it. Some modules here wont work on ALL linux platforms - but on the majority.

There is no cross-platform message-window-solution - which is why I thought of using the one which might be installed on the most desktop linux systems: x11 (and so we can access xset, xmessage ...). If the system call fails we can still print out the message.

I also know that there are other things (confirm, request...) which are not tackled by it but I assume that notify() is among the most used of these unsupported functions.

[GWRon]

OpenUrl-code for Linux contains this (including my recent fix):

	Method OpenURL:Int( url$ ) Override
		'environment variable is most likely set for desktop environments
		'working with the freedesktop.org project / x.org
		'So this works at least for KDE, Gnome and XFCE
		If getenv_("XDG_CURRENT_DESKTOP")
			system_("xdg-open ~q"+url+"~q")
		'Fallback for KDE/GNOME
		ElseIf getenv_("KDE_FULL_DESKTOP")
			system_("kfmclient exec ~q"+url+"~q")
		ElseIf getenv_("GNOME_DESKTOP_SESSION_ID")
			system_("gnome-open ~q"+url+"~q")
		EndIf
	End Method

If wished I could come up with a similar solution for the notifier (try to find "gnome"/"kde" specific commands)