Log Message:
Just include limits.h in Xos_r.h, don't play with _POSIX_SOURCE.
For example, configure plays dirty with that.

Fix a type in the MTSAFE_PWAPI section and the configure test for
NETDBAPI (from David Sainty).

Assume that readdir_r follows POSIX semantics if configure detected it
and we have no reason to believe so otherwise. Most importantly, use it
when _POSIX_REENTRANT_FUNCTIONS is not defined.

Bump revision.