add Copyable from the stdlib to a few tests

If you're using

`-parse-stdlib -module-name Swift`

it's a good idea, but not always required.

Author: kavon

test/NameLookup/stdlib.swift

@@ -1,5 +1,7 @@
 // RUN: %target-typecheck-verify-swift -parse-stdlib -module-name Swift
 
+@_marker protocol _Copyable {}
+
 enum Optional<T> {
   case none
   case some(T)

test/SIL/Parser/self.sil

@@ -1,5 +1,7 @@
 // RUN: %target-swift-frontend %s -parse-stdlib -module-name Swift -emit-silgen | %FileCheck %s
 
+@_marker protocol _Copyable {}
+
 enum Optional<T> {
   case none
   case some(T)

test/SILGen/unmanaged_ownership.swift

@@ -1,6 +1,8 @@
 
 // RUN: %target-swift-emit-silgen -parse-stdlib -module-name Swift %s | %FileCheck %s
 
+@_marker protocol _Copyable {}
+
 class C {}
 
 enum Optional<T> {

test/SILOptimizer/nonescaping_partial_apply_gauntlet.swift

@@ -5,6 +5,7 @@
 // RUN: %target-swift-frontend -emit-sil -parse-stdlib -module-name Swift %s
 // RUN: %target-swift-frontend -emit-sil -O -parse-stdlib -module-name Swift %s
 
+@_marker protocol _Copyable {}
 precedencegroup CastingPrecedence {}
 precedencegroup AssignmentPrecedence {}
 

test/Sema/stdlib_sugar_types.swift

@@ -2,6 +2,8 @@
 
 // RUN: %target-swift-frontend -typecheck -parse-stdlib -module-name Swift -parse-as-library %s
 
+@_marker protocol _Copyable {}
+
 struct Dummy {}
 
 let a: Dummy? = .none

test/attr/attr_availability_osx.swift

@@ -1,6 +1,7 @@
 // RUN: %swift -typecheck -verify -parse-stdlib -module-name Swift -target x86_64-apple-macosx10.10 %s
 
 // Fake declarations of some standard library features for -parse-stdlib.
+@_marker protocol _Copyable {}
 precedencegroup AssignmentPrecedence {}
 enum Optional<T> {
   case none