feat(vector4): optimize vector3 96 bit unpacking
feat(vector4): optimize vector3 96 bit unpacking

A codegen bug in UE 4.23 with clang 3.8 on Android forced the usage of
a different implementation. I took the opportunity to profile various variants
and picked the best for ARMv7 and ARM64.

nfrechette/acl,nfrechette/acl,nfrechette/acl,nfrechette/acl,nfrechette/acl