Profile include support

[Greg Hudson]

On Mon, 2010-08-23 at 14:07 -0400, Sam Hartman wrote:
> Greg, I'm sorry to be difficult, but I believe I may have discovered an
> additional requirement for this package.

No need to apologize; better for this to come up now than later.

> 1) Allow some architecture specific directory such as libdirto be substituted into
> profile include statements.
> 
> 2) Allow some architecture specific directory to be substituted into
> plugin paths.
> 
> 3) Have plugin paths relative to libdir.

I like option 3--or more precisely, the variation of making them
realtive to ${libdir}/krb5/plugins.  There's no use case for shared
object paths being relative to the process's current working directory,
so making them relative to libdir is harmless.  Absolute paths would
still be treated as absolute, of course.