support multiline ellipsification etc. Rather than measuring the text each time we add a character and breaking once it is too long and WORDBREAK is enabled, we copy a whole text segment and then measure it; GetTextExtentPointEx is designed to tell us how much fitted. This may result in a little rescanning if wordbreak is enabled but will be well worth while when multiline path ellipsification is brought down into the NextLine function. Note also that the wordbreak calculation is a little more complete (e.g. including break-within-word for DT_EDITCONTROL).