[0/2] doc: build HTML docs in CI

We are on the move to a restructured text based documentation for U-Boot.
Build target htmldocs is used to transform the restructured text into
HTML. We should avoid syntax errors in the restructured text documents
that may lead to incorrect HTML.

This patch series turns the 'make htmldocs' warnings into errors and adds
build steps for 'make htmldocs' to Travis CI scripts.

I am still working on Gitlab. At least imagemagick (/usr/bin/convert) is
missing in our Docker image.

Heinrich Schuchardt (2):
  doc/Makefile: turn warnings into errors
  travis: build HTML docs

 .travis.yml  | 5 +++++
 doc/Makefile | 1 +
 2 files changed, 6 insertions(+)

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2.25.0