configure.ac: use CPPFLAGS for SSL_OP_NO_TICKET check

AC_EGREP_CPP uses CPPFLAGS, not CFLAGS. Make sure the macro can find
OpenSSL by temporarily adding OPENSSL_CRYPTO_FLAGS to CPPFLAGS.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Heiko Hund <heiko.hund@sophos.com>
Message-Id: <5339EFFC.6090908@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8419
Signed-off-by: Gert Doering <gert@greenie.muc.de>