[PATCH] compat: add canonicalize_file_name

[David Bremner]

David Bremner <david at tethera.net> writes:

> the POSIX 2008 behaviour of realpath is not available everywhere so we
> provide a simple wrapper function.  We use (and provide) the gnu
> extension canonicalize_file_name to make it cleaner to test for the
> feature we need; otherwise we have to rely on realpath segfaulting if
> the second argument is null.

pushed

d