ENH: add HTML Help builder option
Build gallery also for HTML Help docs
Workaround for Sphinx not escaping ``_`` (underscore) for tex output
Merge pull request #3329 from lennart0901/fix_#3326

Workaround for Sphinx not escaping ``_`` (underscore) for tex output
Merge pull request #3325 from cgohlke/patch-1

ENH: add HTML Help builder option
Merge pull request #3324 from mdboom/backend-agg-crash

BUG : fixes memory corruption issues with zero-size rasterized artists

Fix #3304.
Merge branch 'v1.4.x'