Deduce captures(none) for a return place and parameters

Extend attribute deduction to determine whether parameters using
indirect pass mode might have their address captured. Similarly to
the deduction of `readonly` attribute this information facilitates
memcpy optimizations.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -289,6 +289,7 @@ pub(crate) enum AttributeKind {
     DeadOnUnwind = 43,
     DeadOnReturn = 44,
     CapturesReadOnly = 45,
+    CapturesNone = 46,
 }
 
 /// LLVMIntPredicate