switch to non-zero PTHREAD_*_INITIALIZER

[Poul-Henning Kamp]

Right now most of our PTHREAD_*_INITIALIZER macros are defined as NULL.

This is a bad choice from a code quality point of view, because it means
that

	pthread_t my_mutex;

and

	pthread_t my_mutes = PTHREAD_MUTEX_INITIALIZER;

act the same, which they are not.

I suggest that we should change the macros to a non-NULL value, and
add a check for NULL values which emit a warning about the lack of
initialization.

Comments ?

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.