Wrap LLVMConstNamedStruct
Wrap LLVMConstNamedStruct

Allows emission of things like:
```
%Direction = type <{ i2 }>

@Direction.north = global %Direction zeroinitializer
@Direction.east = global %Direction <{ i2 1 }>
@Direction.south = global %Direction <{ i2 -2 }>
@Direction.west = global %Direction <{ i2 -1 }>
```
trill-lang/LLVMSwift