lint mode for int/uint in FFI does not warn about *uint, but should

[nikomatsakis]

Right now if you have an FFI function like:

fn foo(c: *uint, l: uint);

you only get a warning about the variable l, but c is (probably) equally broken. This actually but is in the LLVM bindings, where we translated unsigned * to *uint.

[pcwalton]

Additionally, this should actually be checking the types, not operating on the AST level.

[bstrie]

This still only warns for the second parameter. A more complete test case:

fn main() {}

extern {
    fn foo(c: *uint, l: uint);
}

[metajack]

Still happens. Nominating production ready since FFI is a huge use case.

[graydon]

accepted for production-ready milestone