Update ChangeLog for s/malloc/calloc

ChangeLog

@@ -64,6 +64,8 @@ API Changes
      mbedtls_pk_parse_public_key() and mbedtls_dhm_parse_dhm() now expect the
      length parameter to include the terminating null byte for PEM input.
    * Signature of mpi_mul_mpi() changed to make the last argument unsigned
+   * calloc() is now used instead of malloc() everywhere. API of platform
+     layer and the memory_buffer_alloc module changed accordingly.
    * Change SSL_DISABLE_RENEGOTIATION config.h flag to SSL_RENEGOTIATION
      (support for renegotiation now needs explicit enabling in config.h).
    * net_connect() and net_bind() have a new 'proto' argument to choose