By the time DiagramGraphicDataContext::onCreateContext() completes, we
know if there will be a DrawingML fallback for the SmartArt (called
ExtDrawing in the code) or not.
Warn about this case once at the end of the import when in interactive
mode. Headless mode silently ignores the warning as expected.
Change-Id: I2bfeeedcaa244f08d8a0c208167e79d7bb697e6d
Reviewed-on: https://gerrit.libreoffice.org/33866
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>
ae828495be