limits-fndefn.c and timeouts

limits-fndefn.c takes an impressively long time to run. On an idle machine, -O3 -g -c takes 17:31 and -O2 -g -c takes The test already has a dg-timeout-factor of 4 giving a total timeout of 20 minutes.

Removing the -g brings this down to 30 s. Keeping the -g and adding -fno-var-tracking brings this down to 45 s.

We could bump the multiplier up to 8 but it's getting a bit ridiculous. Any thoughts?

-- Michael