buildroot

package/bullet: new package

[Thomas:
  - move package to 'Libraries -> Graphics'
  - wrap the Config.in help text
  - change license from "Zlib" to "zlib license" to match what the
    zlib package is doing.]

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>