Adds an option to the user preferences panel to turn on text-hinting. Also adds text-hinting support into Blender source code, same way as anti-aliasing.
Note, even though the text is on average slightly more readable after this, it makes words take up noticeably more room.
There are also examples where the words weren't hard to read to begin with.
This impacts the vertical layout for 2.8 where we're often running out of space already.
Since it's a preference we can always change the default, applying.
I've reverted the default back to no hinting temporarily, as it appears this patch was only tested on Linux with newer FreeType versions, while our buildbot and release environments use much older ones. Once FreeType has been upgraded we can change the default again, without that the results look bad.
Even with newer FreeType don't look that great to me, perhaps due to missing subpixel positioning and linear color blending support in BLF.