Add ftdebug.c to thirdparty freetype build.

Allows compilation with -DFT_DEBUG_LEVEL_TRACE to track down buggy fonts.
Fix 695041: add special fast case for 8bpp TIFF predictor.
Fix 695261: separate TM and CTM in outline extraction and stroking steps.

We used to extract the outline using the combined TM*CTM matrix and
use the identity transform for stroking, thus ending up with the wrong
line width.

If we instead extract using the TM and then stroke with the CTM we get
the correct results.