fdo#50763: handle inlined base64 images

Signed-off-by: Andras Timar <andras.timar@collabora.com>

Conflicts:
	sw/source/filter/html/htmlgrin.cxx

Change-Id: I2e9d17dafcf91872d8ea19089e68d8fe652b3e4e
Signed-off-by: Andras Timar <andras.timar@collabora.com>