sigpipe: if mbedTLS is used, ignore SIGPIPE

mbedTLS doesn't have a sigpipe management. If a write/read occurs when
the remote closes the socket, the signal is raised and kills the
application.  Use the curl mecanisms fix this behavior.

Signed-off-by: Jeremie Rapin <j.rapin@overkiz.com>

Closes #3502

lib/sigpipe.h

@@ -7,7 +7,7 @@
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.
 * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
@@ -23,7 +23,8 @@
 ***************************************************************************/
#include "curl_setup.h"

#if defined(HAVE_SIGNAL_H) && defined(HAVE_SIGACTION) && defined(USE_OPENSSL)
#if defined(HAVE_SIGNAL_H) && defined(HAVE_SIGACTION) &&        \
  (defined(USE_OPENSSL) || defined(USE_MBEDTLS))
#include <signal.h>

struct sigpipe_ignore {