adsl/pppoe no longer connecting on 5.1

[Tim Kientzle]

Garrett Wollman wrote:

> alloca() in libc is *fundamentally* broken.  Only the compiler can
> know the current state of the stack frame...


Sounds like alloca() should simply be stricken from libc
on all architectures.

Might also be a good idea to begin removing uses of it.
Searching through the source tree, I note that there's
only a handful of uses of alloca outside of contrib and gnu.

Tim Kientzle