package/netsurf: new package

package/netsurf: new package

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
[Thomas:
 - rename BR2_PACKAGE_NETSURF_FRAMEBUFFER to BR2_PACKAGE_NETSURF_SDL,
   and use "sdl" everywhere instead of "framebuffer", since really SDL
   can display on something else than the framebuffer
 - use a "depends on BR2_PACKAGE_LIBGTK2" instead of a "depends on
   BR2_PACKAGE_XORG7 + many other depends on + select
   BR2_PACKAGE_LIBGTK2"
 - use PKG_CONFIG_HOST_BINARY for the pkg-config path]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>