vmap and StaticVectors

As predicted, `vmap` gives me a tremendous boost in performance =) I'm hitting an error when mapping over static arrays though
```julia
julia> vmap(exp, randn(8));

julia> vmap(exp, @SVector randn(8));
ERROR: conversion to pointer not defined for SArray{Tuple{8},Float64,1,8}
```

Reproduce the reported commands with Julia, comparing vmap(exp, randn(8)) and vmap(exp, @SVector randn(8)). Trace the vmap handling of the SArray input and determine what needs to change so the static-array call completes without the pointer-conversion error; done means the reproduced call succeeds.

Scritto dal modello di indicizzazione a partire dal testo della issue.