[MSPAINT] Use _CrtSetDbgFlag to check memory leak

We can borrow the power of CRT debug. These changes are effective for debug version only:
- Insert #include <crtdbg.h> at main.cpp.
- Call _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF) at the prologue of _tWinMain.

This is a follow-up of #5151 (9abd9b6).
CORE-18867

base/applications/mspaint/main.cpp

@@ -6,10 +6,12 @@
  * PROGRAMMERS: Benedikt Freisen
  */
 
-/* INCLUDES *********************************************************/
-
 #include "precomp.h"
 
+#ifdef _DEBUG
+#include <crtdbg.h>
+#endif
+
 /* FUNCTIONS ********************************************************/
 
 POINT start;
@@ -159,6 +161,11 @@ _tWinMain (HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPTSTR lpszArgument
         0xffffff, 0xffffff, 0xffffff, 0xffffff, 0xffffff, 0xffffff, 0xffffff, 0xffffff
     };
 
+#ifdef _DEBUG
+    /* Report any memory leaks on exit */
+    _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
+#endif
+
     /* init font for text tool */
     ZeroMemory(&lfTextFont, sizeof(lfTextFont));
     lfTextFont.lfHeight = 0;