be somewhat lenient when doing the one-bitmap WMF optimization

The document from bnc#765998 contains a rather huge WMF with poor
quality. It could be smoothscaled to get a much better result,
but doing that would be too slow with an image of this size,
and it would be done every single time the image would need to be
painted, because the resulting image would not be cached.

One reason for this is that the WMF appears to be kinda broken (or let's
say imprecise [which is no wonder after trying to read things like
http://msdn.microsoft.com/en-us/library/dd162607(v=vs.85).aspx
and trying to understand what exactly rlcFrames is supposed to be]).

Change-Id: I017db36ec96f5405ff5965943003d5aa93018a37