parallel-tests: avoid issue with overly long lines in sed input See automake bug#10437: <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10437> and coreutils bug#10427: <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10427#8> * lib/am/check.am (recheck, recheck-html): In order to strip trailing whitespace from the definition of the `$list' variable, we used to invoke sed in a way that could cause it to get passed overly long input lines, causing spurious failures. So rework the logic of the recipe to avoid any sed invocation, relying on simpler shell idioms instead. (check-TESTS): Reorganize the recipe to be more similar to the one of `recheck', for consistency and simplicity. * NEWS: Update. Report and analysis by Paul Eggert.