sci-physics/lammps: Version bump to 2014-06-28.

(Portage version: 2.2.8-r1/cvs/Linux x86_64, signed Manifest commit with key AC91CA52)
Raise minimum linux-headers dependency to >= 3.10 wrt #516086 because it's the first version with IFLA_VLAN_PROTOCOL in include/uapi/linux/if_link.h. Thanks to Maciej Szmigiero for reporting.

(Portage version: 2.2.10/cvs/Linux x86_64, signed Manifest commit with key 4868F14D)
Keyworded on alpha, bug #487178

(Portage version: 2.2.10/cvs/Linux x86_64, signed Manifest commit with key CE5D54E8)