Squashed 'Extern/LuaBridge/' changes from a34416f..351b0b4

351b0b4 Fix linkage specification for identity key function (closes issue #42)
193bc53 Fix whitespace and style

git-subtree-dir: Extern/LuaBridge
git-subtree-split: 351b0b4993f730b58c865136ad858a9267825bb8
Merge commit '9bcf7672aa50f3ae9d5438fea137198877fd7e78' into develop