Make `MaybeStorageLive` correct for all kinds of MIR bodies
Make `MaybeStorageLive` correct for all kinds of MIR bodies

Before, it ignored the first argument and marked all variables without
`Storage*` annotations as dead.

graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust