FreeBSD port (36): config support

[Roland McGrath]

> I want glibc to coexist with FreeBSD libc, assuming they are installed in
> different directories. For the moment I assume the user will be responsible
> for not mixing libraries of the two universes in the same directory, and
> for using LD_LIBRARY_PATH with moderation.
[...]
> Both native FreeBSD libraries and glibc-linked libraries have the same ELF
> headers; the distinction will therefore come from the libc.so that a library
> is linked with, like it was done to distinguish libc.so.5 and libc.so.6 on
> Linux/{i386,m68k} a few years ago.

If you are using /usr/libexec/ld-elf.so.1 as the program interpreter name
then it seems ill-advised to use a soname that is likely to one day
conflict with the native FreeBSD libc's soname.  When FreeBSD reaches 
libc.so.6, then your scheme for distinguishing native and glibc soname
dependencies will break down.