Consolidating text layout code

[Chris Sherlock]

Hi all,

I have migrated text layout code from OutputDevice and into a TextLayoutHelper 
class. This is because OutputDevice’s primary purpose is not working out text 
layout, and in fact this is what we are attempting to do with the ITextLayout 
interface.

Can anyone have a look at https://gerrit.libreoffice.org/c/core/+/157362 for 
review? 

Thanks all!
Chris
Sent from my iPhone