When using pthread_once with destructors they are only called,
if each thread (including the main thread) is exited with pthread_exit.
Introducing winpr_exit as a wrapper for that purpose.
libwinpr-tools is a replacement for winpr-makecert-tool.a. Currently
it's basically the same as winpr-makecert-tool.a but in future
functionality that doesn't fit directly in winpr will be added here.
