Added support for autoconf

I was frustrated by WAF since I couldn't find a version that would be able to build the library. So I spent some time to come up with an autoconf-based build.

The library builds correctly on MacOS X 10.9. The unittests pass with the exception of 3 of them:

- whisperlib/http/test/http_request_test.sh: there are some failing diffs.
- whisperlib/net/test/dns_resolver_test: the DNS lookup fails, but the test program should not CHECK. I'll fix it later on.
- whisperlib/http/test/test_failsafe.sh: I'm not sure what's going on here, maybe you can take a look.