[libcxx] [test] Rename _Tp to T. NFCI.

This improves readability and (theoretically) improves portability,
as _Ugly names are reserved.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@310758 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/language.support/support.limits/limits/numeric.limits.members/const_data_members.pass.cpp

@@ -37,8 +37,8 @@
         round_style
 */
 
-template <class _Tp>
-void test(const _Tp &) {}
+template <class T>
+void test(const T &) {}
 
 #define TEST_NUMERIC_LIMITS(type) \
   test(std::numeric_limits<type>::is_specialized); \