curl: enable wrongly disabled HTTP_AUTH

curl: enable wrongly disabled HTTP_AUTH

commit ea66e463cffc0811757eedee80889323ff66191c added a new config
option LIBCURL_HTTP_AUTH to enable or disable HTTP_AUTH support in
cURL. It defaulted the option to n (disabled).

However, prior to this change HTTP_AUTH was enabled for cURL, as the
configure script defaults to HTTP_AUTH enabled when it is not
explicitly disabled.

This impacts any consumer of cURL that uses HTTP_AUTH, including
authentication by username and password in the URL. (Confirmed via
run testing).

So we set the default for the option to y (enabled).

Signed-off-by: Daniel F. Dickinson <dfdpublic@wildtechgarden.ca>