Apply noundef attribute to &T, &mut T, Box<T>, bool

This doesn't handle `char` because it's a bit awkward to distinguish it
from u32 at this point in codegen.

Note that for some types (like `&Struct` and `&mut Struct`),
we already apply `dereferenceable`, which implies `noundef`,
so the IR does not change.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -189,6 +189,7 @@ pub enum Attribute {
     StackProtectReq = 30,
     StackProtectStrong = 31,
     StackProtect = 32,
+    NoUndef = 33,
 }
 
 /// LLVMIntPredicate