Resolves: i123564 corrected some aspects when working with bitmaps...

with low color depth or small size

(cherry picked from commit ba54ce4fc788605fc96235f432b455311faee406)

Conflicts:
	cui/source/tabpages/tpbitmap.cxx

Change-Id: I10677414ab7d1904dbb29cd395a0c0334e0faa03