Merge branch 'ng/many-tests' into ng/master

* ng/many-tests:
  [ng] check: in recipes, don't use pipe when redirection suffices
  [ng] recheck: don't exceed command line limits, even with many failed tests
  [ng] coverage: recheck with many failed tests
  [ng] check: refactor for less duplication and better performances
  [ng] check: use awk rather than grep+xargs to count test results
  [ng] parallel-tests: do not exceed command line length limits
  [ng] coverage: testing with lots of test scripts

diff --cc Makefile.am
Simple merge

diff --cc lib/am/clean.am
Simple merge

diff --cc lib/am/header-vars.am
Simple merge

diff --cc lib/am/parallel-tests.am
Simple merge