Add support for explicit_memset
* configure.ac: Add function check for 'explicit_memset'. * src/misc.c (_gcry_fast_wipememory, _gcry_fast_wipememory2): Use explicit_memset if available.
- GnuPG-bug-id: D476
- Reported-by: <devnexen@gmail.com>
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>