WIN32 cleanup (updated version)

Some &vec[0] when vec is empty fixes.
Merged win32+{botan,openssl} into win32 and wrote a Configure script in two versions (one in perl (more for OpenSSL) and one in python2 (more for Botan)).
Tested for the standard configs (i.e., the 2 supported before).
Updated the doc (aka WIN32-NOTES.md).

So a bit more than the previous request but based on the last develop.