pthread is not by default in Windows.

Either: - add installation instructions in README - disable prepos_mutex.h in mili.h until support is added - ifdef implementatino of prepos_mutex and implement it in Windows

The prepos_xxxx.h files are provided as examples rather than usable files (in fact, they are not included from mili.h). I propose just to not use this file (and the test) under windows. This file is nowhere used currently.