SDF module ready for integration

[Werner LEMBERG]

Anuj,


I've polished your SDF driver; see the 'sdf' branches in both the
'freetype2' and 'freetype2-demos' repositories.  Basically, it's ready
to be merged with 'master' :-)

Note, however, that there is a problem with the graphics display: On
Linux, something has changed in the graphics driver of the demos –
instead of a single image I get four, with stripes (see attached
image).  For testing purposes I've also rebased my new branches at the
same commits as the original 'GSoC-2020-anuj' branches, and the
display is then identical (i.e., good).  In other words, the problem
is indeed in FreeType master...

Please have a look (and Alexei, please you, too)!


    Werner