i'd prefer to go a step further, and not only convert pdf and svg files to png,
but everything (with the possible exception of jpg files), as most other image
-formats can't be displayed in a browser anyway.
+formats can't be displayed in a browser anyway -- but i didn't in this patch
+series, as it would alter the file names of existing images, i don't know if
+that needs special care or breaks something i don't use; this way, my patches
+should be safe for inclusion.
--[[chrysn]]