Fix unused parameters and variables

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@290459 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/string b/include/string
index 840fd00..2e5ffc1 100644
--- a/include/string
+++ b/include/string
@@ -2220,7 +2220,7 @@
 }
 
 template <class _Tp1, class _Tp2>
-bool __ptr_in_range (const _Tp1* __p, const _Tp2* __first, const _Tp2* __last)
+bool __ptr_in_range (const _Tp1*, const _Tp2*, const _Tp2*)
 {
     return false;
 }