verbose testsuite output contains 1M newlines

[Ralf Wildenhues]

Hello Eric,

running
  make check-local TESTSUITEFLAGS=-v

on M4 (git master) produces lots of output on GNU/Linux/bash.  More
precisely, the AT_CHECK in builtins.at:470 causes 1024*1024 newlines
to be output, and I think there are more instances later.  Can this
easily be avoided?

Hmm, maybe this is introduced by some Autotest changes in Autoconf even.

Cheers, and thanks,
Ralf