Changes:
  * OT/TTF: Fix color inversion on Kindle <= 4 when rendering in B&W
  * OT/TTF: Try harder to deal with fonts with broken metrics (fix crashes with broken ascend)
  * OT/TTF: Limited the amount of glyph lookups, for a minor speedup, especially for fonts with a large Unicode coverage (CJK, f.g.)
  * OT/TTF: Fixed the hard-break fallback when the linebreaking algorithm can't find a typographically sane break (fix borken behavior when, f.g., printing a single block of text wider than a single line).
  * CLI: Properly enable OT rendering when asked to, even when reading data from stdin
  * Assume both variants of the Kobo H2O² have an inverted panel, like the H2O & AuraHD, because that seems to be the consensus. Give me a shout is stuff is upside down in 16bpp modesets.
  * OT/TTF: Support negative margins, making it easier to align stuff to the bottom-right corner of the screen without having to do the maths yourself.
  * Passing an empty region to -s, --refresh (or to fbink_refresh for API users) will now do a full-screen refresh
  * Allow skipping the actual eInk refresh via -b, --norefresh (useful when drawing in batch)

API Changes:
  * top, bottom, left & right fields of the margins struct of FBInkOTConfig are now signed (short int instead of unsigned short int).
  * Added no_refresh field to FBInkCOnfig struct, used to skip eInk refreshes altogether (can be of use when drawing in batch).