Add --with-warn option to configure, making it easy to
select between a couple of predefined warning options.

Having all warnings on and treated as errors wasn't so good,
since different versions of gcc have different warnings.
There's no need to make it harder than it should be to build
btpd.

* Change email address.
* Better tests for curl.

git-svn-id: file:///home/rnyberg/svngit/btpd/releases/0.1@1 76a1f634-46fa-0310-9943-bd1476092a85