TS-2271: Change the OpenSSL init + callbacks to use raw pthread functions
TS-2271: Let TSHttpTxnReenable work gracefully when it's called from an unexpected thread (this_ethread() returns NULL).
TS-2271: update CHANGES
TS-2465: libxml2 detection broken

There is problem with libxml2 detection in configure script. It
inserts library path into ld options without any prefix causing any
next compile attempts to fail. Tested on freebsd 10.0