Add evhtp_thr and ws headers to install
Accessors for conn, uri, thread, and path.

I also converted EXPORT_SYMBOL in the source to EVHTP_EXPORT in the
headers.
move EVHTP_EXPORT before includes
fix test_query example
Fix test_vhost build
Fix thread_design build
Merge pull request #150 from zerotao/libevhtp2_acessors

Libevhtp2 acessors