fsusage: dynamic statvfs() check incorrect for Debian 7.0

[Eric Wong]

Debian testing (7.0) builds eglibc 2.13 against Linux 2.6.26 features
so it can run as a chroot on older Debian releases.

Debian 7.0 will ultimately use a 3.2 kernel, Debian 6.0 runs 2.6.32.

So I think the highest kernel version Debian can currently build eglibc
against is is 2.6.32 (so it can still run as a chroot on Debian 6.0
systems), but statvfs() needs a glibc built with Linux 2.6.36 features.

So I think the correct solution would be to check the __ABI_TAG_VERSION
in the PT_NOTE section, but I haven't figured out how to do that at
runtime...  (ref: csu/abi-note.S in glibc source tree).

ref:

commit c25bdbae48977a527dff69150f59fb0746d31b51
Author: Paul Eggert <address@hidden>
Date:   Fri May 11 20:54:15 2012 -0700

    fsusage: check for GNU/Linux statvfs problem dynamically