As we upgrade or replace the SVG renderer, it would be nice to be able to easily force all
rasterized SVGs to get rerendered using the new version, thus more or less automatically
cleaning up glitched renderings.

A likely easy possibility is an epoch timestamp similar to $wgCacheEpoch; when checking for
thumbnail file existence, the date could also be compared. Or some such.

Version: 1.6.x
Severity: normal