fextl: Implement stack

External/FEXCore/include/FEXCore/fextl/stack.h

@@ -0,0 +1,10 @@
+#pragma once
+#include <FEXCore/fextl/allocator.h>
+#include <FEXCore/fextl/deque.h>
+
+#include <stack>
+
+namespace fextl {
+  template<class T, class Container = fextl::deque<T>>
+  using stack = std::stack<T, Container>;
+}