Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add `_PATH_DEVZERO'.
Use _PATH_* where where possible.

Remove trailing whitespace.

This commit was generated by cvs2svn to compensate for changes in r1905,
which included commits to RCS files with non-trunk default branches.

Sun RPC demo programs from 4.4-Lite