fix libcrypto detection in openssl 1.1+ without pkg-config

CRYPTO_lock() was removed. test for X509_cmp() instead, which we
actually use.

inspired by report from FX <coudert@users.sourceforge.net>.

configure.ac

@@ -94,7 +94,7 @@ if test "x$ob_cv_with_ssl" != xno; then
     sav_LDFLAGS=$LDFLAGS
     LDFLAGS="$LDFLAGS $SSL_LDFLAGS"
     AC_CHECK_LIB(dl, dlopen, [LIBDL=-ldl])
-    AC_CHECK_LIB(crypto, CRYPTO_lock, [LIBCRYPTO=-lcrypto])
+    AC_CHECK_LIB(crypto, X509_cmp, [LIBCRYPTO=-lcrypto])
     AC_CHECK_LIB(ssl, SSL_connect,
                  [SSL_LIBS="-lssl $LIBCRYPTO $LIBDL" have_ssl_paths=yes])
     LDFLAGS=$sav_LDFLAGS