media-plugins/grilo-plugins: bump to 0.3.8

media-plugins/grilo-plugins: bump to 0.3.8

Instead of gmime, totem-pl-parser is now used for that, moving
the non-optional dep to that. Due to that, various optional
plugins are now just always built, as they only had pl-parser
missing. libsoup is also more widely needed (by a plugin that
wasn't optional before); just hard depend on that too, making
some more plugins always built, as option would be redundant.

Help files are installed with slot suffix now, instead of
messing with the XML filenames. It doesn't look like they are
properly usable in yelp either way (only seems to work if
opened up with full path).

Package-Manager: Portage-2.3.52, Repoman-2.3.12
Signed-off-by: Mart Raudsepp <leio@gentoo.org>