Add support for newer APIs

The API world hasn't been frozen over the years and POSIX
nowadays defines some new APIs which we might want to start exploring.

This patch adds support for the following new APIs:

fchown()/lchown() replacing the chown call.
fchmod()/lchmod() replacing the chmod call.
utimes()/futimes()/futimens()/lutimes() replacing the utime call.

If those APIs are available they are prefered rather then using the
standard chown(), chmod() and utime() APIs.

We move away from using utime when possible because POSIX.1-2008
marks utime() as obsolete.
Rebuild configure and config.h.in
Backport some obvious fixes for the core from Bacula 7.