Final plugin update for 6.4

Barring any surprises or critical bug-fixes, this should be the last
plugin update before 6.4 releases.

ExifTool is now v9.69 and the author is on holiday for August, so this
version will have to do.

FreeImage is custom-compiled based off the latest 3.16.1 code, as there
are a number of important bugfixes from 3.16.0.