Allocators cleanup

Move xalloc.h to xrCore/Memory folder
Remove unused doug_lea_memory_allocator.* from xrRender and xrServerEntities
Remove unused ptmalloc3 allocator
Move dlmalloc to xrCore/Memory folder
xrCore project file:
- Move Memory manager and Memory monitor folders to Memory folder

Author: Xottab-DUTY

Externals/OPCODE/pch.hpp

@@ -4,7 +4,7 @@
 
 #include "Common/Common.hpp"
 #include "xrCore/xrCore.h"
-#include "xrCore/doug_lea_allocator.h"
+#include "xrCore/Memory/doug_lea_allocator.h"
 #include "xrCore/memory_allocator_options.h"
 
 #ifdef USE_ARENA_ALLOCATOR

src/Layers/xrRender/RenderAllocator.hpp

@@ -1,4 +1,4 @@
 #pragma once
-#include "xrCore/doug_lea_allocator.h"
+#include "xrCore/Memory/doug_lea_allocator.h"
 
 extern doug_lea_allocator g_render_allocator;