Animation Subset End Frame can be set beyond Final Frame

[c-lipka]

Setting the options +kfi4 +kff4 +sf3 +ef5 will currently cause frames 4 and 5 to be rendered.

[c-lipka]

For the records: As this is presumably long-standing behavior, and some people might actually be making use of it, we probably don't want to change it as we're preparing for v3.8.0 release.