Log Message:
Initial import of Bruce Guenter's syncdir library. In order to
portably create the shared library, I've libtoolized it (tested on
NetBSD 2.0_BETA and Darwin 7.5.0).

syncdir is a small library that makes the link() system call
synchronous. This is necessary when using qmail with the queue on
a filesystem that doesn't perform link() synchronously, such as
Linux's ext2fs, Reiserfs, SGI's XFS, and BSD FFS with softupdates.