Re: conditional compilation (or: makefiles again)

Updating libc may be harder than you think, it does some funny stuff that
we would not like to redesign.  If you can submit changes that make it
compatible with both 2.13 and 2.53 then that will definitely be fine.  But
it is not a priority at all for libc because a new Autoconf release (after
a long period of neglect) was made massively incompatible with the
long-stable version apparently without regard for users, and we are not
bending over to change just for change's sake.