support for FreeBSD and GNU/FreeBSD

[Bruno Haible]

David O'Brien writes:

> I'm afraid I'm going to have to put on my FreeBSD hat and strongly state
> that EI_OSABI==ELFOSABI_FREEBSD is what should be the default.

Ok, I can resend my patch with a different default behaviour (to
prefer the new branding mode if no FreeBSD version number was given).

OTOH, can you implement H.J.'s suggestion to look at the .note.ABI-tag
ELF section in the kernel? The GNU/FreeBSD port of glibc uses the
following definition:

# Configuration		ABI OS	ABI version
# -------------		------	-----------

.*-.*-freebsd.*-gnu.*	3	4.0.0	# earliest compatible kernel version

This means the section contents looks like this:

 04000000 10000000 01000000 474e5500  ............GNU.
 03000000 04000000 00000000 00000000  ................

Bruno