[libc++] Rename function parameters to avoid shadowing.

[STL_MSFT]

Summary

[libc++] Rename function parameters to avoid shadowing.

Fixes MSVC "warning C4459: declaration of 'meow' hides global declaration".

[EricWF]

r267838.

test/std/thread/futures/futures.async/async.pass.cpp

int& f1()
     return i;
 }
 
 void f2()
 {
     std::this_thread::sleep_for(ms(200));
 }
 
-std::unique_ptr<int> f3(int i)
+std::unique_ptr<int> f3(int j)
 {
     std::this_thread::sleep_for(ms(200));
-    return std::unique_ptr<int>(new int(i));
+    return std::unique_ptr<int>(new int(j));
 }
 
 std::unique_ptr<int> f4(std::unique_ptr<int>&& p)
 {
     std::this_thread::sleep_for(ms(200));
     return std::move(p);
 }
 
-void f5(int i)
+void f5(int j)
 {
     std::this_thread::sleep_for(ms(200));
-    throw i;
+    throw j;
 }
 
 int main()
 {
     {
         std::future<int> f = std::async(f0);
         std::this_thread::sleep_for(ms(300));
         Clock::time_point t0 = Clock::now();