Don't use non-standard header for C11/C++17 aligned_alloc()

$ c++ -std=c++11 src/*.cpp -lvulkan
In file included from src/VmaUsage.h:35:0,
                 from src/VmaUsage.cpp:8:
src/vk_mem_alloc.h:2233:47: fatal error: malloc.h: No such file or directory
     #include <malloc.h> // for aligned_alloc()
                                               ^

Author: jbeich

src/vk_mem_alloc.h

@@ -2229,10 +2229,6 @@ remove them if not needed.
 #include <mutex> // for std::mutex
 #include <atomic> // for std::atomic
 
-#if !defined(_WIN32) && !defined(__APPLE__)
-    #include <malloc.h> // for aligned_alloc()
-#endif
-
 #ifndef VMA_NULL
    // Value used as null pointer. Define it to e.g.: nullptr, NULL, 0, (void*)0.
    #define VMA_NULL   nullptr