Incompatible with Thunderbird 63

[1ec5]

AVIM is incompatible with Thunderbird 63. As of version 63, legacy addons either have to make use of a stopgap XUL overlay loader via a manifest.json or become restartless (#9).

[1ec5]

Thunderbird 63 removes <listbox>, which is used in the blacklist preference pane, in favor of <richlistbox>.

https://github.com/1ec5/avim/blob/bbd494130f5e18d3d9c24c6d9a348754d1271f8e/content/blacklist.xul#L39

<stringbundleset> and <stringbundle> have also been removed in favor of Services.strings.createBundle(), though the restartless work in #132 wound up removing string bundle usage anyways.

[1ec5]

At least in my local setup, it was pretty straightforward to adopt the XUL overlay loader, though I don’t know what effect the manifest.json will have on older versions of Thunderbird that natively support both legacy and restartless add-ons. It was also necessary to remove a couple other compatibility shims for older versions of Gecko, so it’s likely that supporting Thunderbird 63 and above will require dropping support for Firefox 2–3 and the equivalent Thunderbird versions.

The frame script now loads, but it doesn’t seem to be able to find an nsIEditor for some reason. It could be that Gecko has quietly removed some interface usage that AVIM depends on without removing the interfaces themselves.