[oe] Add gtksourceview 2.x and rename the 1.x tree recipe

[Elena Grandi]

GtkSourceView[1] currently maintains a stable 2.x tree and an old stable
1.x tree for compatibility with older applications[2] and they can be
installed together on a computer.

I need to add the recipe for the latest 2.x version, and since the old
stable is used just in 2 recipes (gobby_0.4.1.bb and tea_17.3.5.bb) and
mentioned as a preferred version in preferred-om-2008-versions.inc
it seems to me that this could be a good time to rename it to
gtksourceview1 with minimal breakage.

(I also hope I've used correctly the git tools for patch sending by
email: sorry if I've done something wrong)

[1] http://projects.gnome.org/gtksourceview/
[2] http://projects.gnome.org/gtksourceview/download.html

--
Elena ``of Valhalla'' Grandi

email: elena.valhalla at gmail.com