Merge branch 'ls/travis-doc-asciidoctor' into maint

Travis CI gained a task to format the documentation with both
AsciiDoc and AsciiDoctor.

* ls/travis-doc-asciidoctor:
travis-ci: check AsciiDoc/AsciiDoctor stderr output
travis-ci: unset compiler for jobs that do not need one
travis-ci: parallelize documentation build
travis-ci: build documentation with AsciiDoc and Asciidoctor

diff --cc .travis.yml
index 6dd73d1f02bd0a795fc706c82020d459b2cea49e,e5e7c3edd78209467ab9dc7032138db46ded8190..278943d14a244b6b748078ff9ee18a17f58e7b45
--- 1/.travis.yml
--- 2/.travis.yml
+++ b/.travis.yml
@@@ -39,24 -39,9 +39,25 @@@ env
  
  matrix:
    include:
 +    - env: GETTEXT_POISON=YesPlease
 +      os: linux
 +      compiler:
 +      addons:
 +      before_install:
 +    - env: Windows
 +      os: linux
 +      compiler:
 +      addons:
 +      before_install:
 +      before_script:
 +      script:
 +        - >
 +          test "$TRAVIS_REPO_SLUG" != "git/git" ||
 +          ci/run-windows-build.sh $TRAVIS_BRANCH $(git rev-parse HEAD)
 +      after_failure:
      - env: Linux32
        os: linux
+       compiler:
        services:
          - docker
        before_install:
@@@ -77,21 -61,9 +78,21 @@@
          # Use the following command to debug the docker build locally:
          # $ docker run -itv "${PWD}:/usr/src/git" --entrypoint /bin/bash daald/ubuntu32:xenial
          # root@container:/# /usr/src/git/ci/run-linux32-build.sh
 +    - env: Static Analysis
 +      os: linux
 +      compiler:
 +      addons:
 +        apt:
 +          packages:
 +          - coccinelle
 +      before_install:
 +      script:
 +        # "before_script" that builds Git is inherited from base job
 +        - make coccicheck
 +      after_failure:
      - env: Documentation
        os: linux
-       compiler: clang
+       compiler:
        addons:
          apt:
            packages: