[OE-core] [ANNOUNCE] Devshell Usage Change

[Chris Larson]

Saul reminded me that I never sent a proper email to let people know about the
usability change to devshell, so only those who reviewed the commits
know about it.

In the new implementation, a single OE_TERMINAL variable controls the behavior.

When using 'auto', or requesting an unsupported terminal, we attempt to spawn
them in priority order until we get one that's available on this system (and
in the case of the X terminals, has DISPLAY defined).  The 'none' value is
used when we're doing things like automated builds, and want to ensure that no
terminal is *ever* spawned, under any circumstances.

Current available terminals (in addition to 'noop' and 'auto'):

    gnome
    konsole
    xterm
    rxvt
    screen

Examples:

    OE_TERMINAL = "xterm"
    OE_TERMINAL = "noop"
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphi