package/libsoil: new package

Needed for these new Kodi addons:

kodi-screensaver-asterwave
kodi-screensaver-cpblobs
kodi-screensaver-matrixtrails
kodi-screensaver-planestate
kodi-visualisation-fountain

[Thomas:
 - don't pass LIBSOIL_CFLAGS since this variable no longer exists.
 - pass TARGET_CONFIGURE_OPTS on the right hand side of make for the
   install steps, like was done for the build step.]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>