move m_burn and function attributes to dbhelpers

use m_burn for libtomcrypt zeromem() too

libtomcrypt/src/headers/tomcrypt_custom.h

@@ -1,7 +1,7 @@
 #ifndef TOMCRYPT_CUSTOM_H_
 #define TOMCRYPT_CUSTOM_H_
 
-/* this will sort out which stuff based on the user-config in options.h */
+/* compile options depend on Dropbear options.h */
 #include "options.h"
 
 /* macros for various libc functions you can change for embedded targets */

libtomcrypt/src/misc/zeromem.c

@@ -9,6 +9,7 @@
  * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
  */
 #include "tomcrypt.h"
+#include "dbhelpers.h"
 
 /**
    @file zeromem.c
@@ -22,11 +23,7 @@
 */
 void zeromem(void *out, size_t outlen)
 {
-   unsigned char *mem = out;
-   LTC_ARGCHKVD(out != NULL);
-   while (outlen-- > 0) {
-      *mem++ = 0;
-   }
+   m_burn(out, outlen);
 }
 
 /* $Source: /cvs/libtom/libtomcrypt/src/misc/zeromem.c,v $ */