Make some automatic variables, which will be needed by other threads,
into statics. This avoids uneeded data structures to communicate this
data into threads.

SSL_CTX is reference counted and thread safe (if not modified). Keep a
copy in an automatic variable to lose our reference via
free_ssl_ctx()->SSL_CTX_free.

We want to process each client in a individual thread. This requires a
separate function per client. Factor that out.

Use mutex to protect shadow_buf and statbuf.

As clients are handled in individual threads now, individual client or
communication problems can no longer spoil the game for other clients,
so relace the timeout for client responses.

Increase timeout so we have a better chance to get through short network
problems or server overload conditions.

Always return some more or less sensible value in errno for failing
functions.

We want libnss_mxshadow.c and get_shadow_line.c in a single compilation
unit, so that the preprocessor macros are in the same namespace.

Include get_shadow_line.c from source not from the command line.

Do not assume that stderr is available for logging, because the calling
application might reuse fd2 for antohter purpose (at least in theorie).
Redirect diagnostincs to syslog.

We include get_shadow_line.c, we don't link against it. Remove uneeded
target.

Remove obsolete test script.

0.3