Make coap_pdu-t independent of the header style.
Use C99 sized types when applicable.
Use transaction ids in host byte order in the library.
Make coap_pdu_t payload storage grow on demand.
Add parsing and encoding of PDUs with UDP or TCP style headers.
Adapt examples and unit tests to the new PDU format.
Merge changes from PR #47 related to windows platform support.
Add full windows platform support including correct error checking and working regression tests and examples.
Remove need to build applications using libcoap with -DWITH_POSIX and to include coap_config.h. This applies to the examples as well.