[libc++] Make the naming of private member variables consistent and enforce it through readability-identifier-naming

Reviewed By: ldionne, #libc

Spies: aheejin, sstefan1, libcxx-commits

Differential Revision: https://reviews.llvm.org/D129386

NOKEYCHECK=True
GitOrigin-RevId: 84fc2c3cd62ab5be51d65f818854bb031b74c0f2
diff --git a/src/memory.cpp b/src/memory.cpp
index bf96efa..2dcbb35 100644
--- a/src/memory.cpp
+++ b/src/memory.cpp
@@ -152,21 +152,21 @@
 };
 
 _LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) noexcept
-   : __lx(p)
+   : __lx_(p)
 {
 }
 
 void
 __sp_mut::lock() noexcept
 {
-    auto m = static_cast<__libcpp_mutex_t*>(__lx);
+    auto m = static_cast<__libcpp_mutex_t*>(__lx_);
     __libcpp_mutex_lock(m);
 }
 
 void
 __sp_mut::unlock() noexcept
 {
-    __libcpp_mutex_unlock(static_cast<__libcpp_mutex_t*>(__lx));
+    __libcpp_mutex_unlock(static_cast<__libcpp_mutex_t*>(__lx_));
 }
 
 __sp_mut&