Get rid of NULLs in core/

core/fxcrt/include/fx_system.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef CORE_FXCRT_INCLUDE_FX_SYSTEM_H_
 #define CORE_FXCRT_INCLUDE_FX_SYSTEM_H_
 
 #include <assert.h>
@@ skipping 73 matching lines @@
 
 #ifndef FALSE
 #define FALSE 0
 #endif
 
 #ifdef __cplusplus
 static_assert(TRUE == true, "true_needs_to_be_true");
 static_assert(FALSE == false, "false_needs_to_be_false");
 #endif
 
-#ifndef NULL
-#define NULL 0
-#endif
-
 #ifndef ASSERT
 #ifndef NDEBUG
 #define ASSERT assert
 #else
 #define ASSERT(a)
 #endif
 #endif
 
 #if defined(__clang__) || defined(__GNUC__)
 #define PDFIUM_IMMEDIATE_CRASH() __builtin_trap()
@@ skipping 224 matching lines @@
 
 // Prevent a function from ever being inlined, typically because we'd
 // like it to appear in stack traces.
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 #define NEVER_INLINE __declspec(noinline)
 #else  // _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 #define NEVER_INLINE __attribute__((__noinline__))
 #endif  // _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 
 #endif  // CORE_FXCRT_INCLUDE_FX_SYSTEM_H_