Fix release build after recent fix for debug one

It's becoming annoying to have public API dependent on build type
and everything. Let's just always have API defined and do stubs
in the function implementation instead.

source/blender/blenlib/BLI_system.h

@@ -21,11 +21,14 @@
 #ifndef __BLI_SYSTEM_H__
 #define __BLI_SYSTEM_H__
 
+#include <stdio.h>
+
 /** \file BLI_system.h
  *  \ingroup bli
  */
 
 int BLI_cpu_support_sse2(void);
+void BLI_system_backtrace(FILE *fp);
 
 /* getpid */
 #ifdef WIN32

source/blender/blenlib/BLI_utildefines.h

@@ -633,7 +633,7 @@ extern bool BLI_memory_is_zero(const void *arr, const size_t arr_size);
  * for aborting need to define WITH_ASSERT_ABORT
  */
 #ifndef NDEBUG
-extern void BLI_system_backtrace(FILE *fp);
+#  include "BLI_system.h"
 #  ifdef WITH_ASSERT_ABORT
 #    define _BLI_DUMMY_ABORT abort
 #  else

source/blender/makesrna/intern/makesrna.c

@@ -50,7 +50,7 @@
 #ifndef NDEBUG
 void BLI_system_backtrace(FILE *fp)
 {
-	(void)fp;
+       (void)fp;
 }
 #endif