update-all-config.pl: switch from qx to pipe

update-all-config.pl: switch from qx to pipe

In cases where there are unfortunately a vast number of fixes
needed, collecting them all at once does not behave nicely with
regard to memory usage.

Instead read the results from a pipe and process them as they
come in to avoid the problem.

This actually does run just a bit slower than the all-at-once
technique, but it still runs much, much faster than the .sh
version did.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>