Fix out-of-the-box builds with no OpenSSL (#633)

Don't make OpenSSL detection error out unless --with-openssl explicitly given.

This fixes the out-of-the-box build on macOS, which doesn't include
headers, etc. for OpenSSL by default.  The configure script still
errors out if the user specifies a --with-openssl flag but for some
reason the build host's OpenSSL is broken or can't be used.

* Regen.
diff --git a/configure b/configure
index 81bc819..7d2de4e 100755
--- a/configure
+++ b/configure
@@ -12947,10 +12947,12 @@
 
             { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
-             { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+             if test "x$with_openssl" != "x"; then
+	  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "--with-openssl was given, but test for openssl failed
+as_fn_error $? "--with-openssl was given, but test for OpenSSL failed
 See \`config.log' for more details" "$LINENO" 5; }
+	  fi
 
 
 fi