[libc++] Fix warnings when compiling libc++ for Windows with clang-cl /W4

Differential Revision: https://reviews.llvm.org/D96408

Author: ColinFinck

libcxx/src/atomic.cpp

@@ -147,7 +147,7 @@ static void __libcpp_contention_notify(__cxx_atomic_contention_t volatile* __con
         // We only call 'wake' if we consumed a contention bit here.
         __libcpp_platform_wake_by_address(__platform_state, __notify_one);
 }
-static __cxx_contention_t __libcpp_contention_monitor_for_wait(__cxx_atomic_contention_t volatile* __contention_state,
+static __cxx_contention_t __libcpp_contention_monitor_for_wait(__cxx_atomic_contention_t volatile* /*__contention_state*/,
                                                                __cxx_atomic_contention_t const volatile* __platform_state)
 {
     // We will monitor this value.

libcxx/src/support/win32/locale_win32.cpp

@@ -17,8 +17,8 @@ int __libcpp_vasprintf(char **sptr, const char *__restrict fmt, va_list ap);
 
 using std::__libcpp_locale_guard;
 
-// FIXME: base currently unused. Needs manual work to construct the new locale
-locale_t newlocale( int mask, const char * locale, locale_t /*base*/ )
+// FIXME: base and mask currently unused. Needs manual work to construct the new locale
+locale_t newlocale(int /*mask*/, const char * locale, locale_t /*base*/)
 {
     return {_create_locale( LC_ALL, locale ), locale};
 }