70f6d16ae2
Also adds support for extern functions, simple pointer and simple array
types and values.
A simple hello world now compiles:
`zig build-exe example.zig -fLLVM -lc`
```
extern fn puts(s: [*:0]const u8) c_int;
export fn main() c_int {
_ = puts("hello world!");
return 0;
}
```