Merge branch 'es/chainlint'

Revamp chainlint script for our tests.

* es/chainlint:
  chainlint: colorize problem annotations and test delimiters
  t: retire unused chainlint.sed
  t/Makefile: teach `make test` and `make prove` to run chainlint.pl
  test-lib: replace chainlint.sed with chainlint.pl
  test-lib: retire "lint harder" optimization hack
  t/chainlint: add more chainlint.pl self-tests
  chainlint.pl: allow `|| echo` to signal failure upstream of a pipe
  chainlint.pl: complain about loops lacking explicit failure handling
  chainlint.pl: don't flag broken &&-chain if failure indicated explicitly
  chainlint.pl: don't flag broken &&-chain if `$?` handled explicitly
  chainlint.pl: don't require `&` background command to end with `&&`
  t/Makefile: apply chainlint.pl to existing self-tests
  chainlint.pl: don't require `return|exit|continue` to end with `&&`
  chainlint.pl: validate test scripts in parallel
  chainlint.pl: add parser to identify test definitions
  chainlint.pl: add parser to validate tests
  chainlint.pl: add POSIX shell parser
  chainlint.pl: add POSIX shell lexical analyzer
  t: add skeleton chainlint.pl