Tank Companion

### Fixed
- **WoW Forever is recognised on every Forever client.** It was told apart by
  interface 16001 and by the game reporting itself as the retail version. A
  Forever client that reports otherwise was taken for neither game, so no
  class kit loaded and the addon sat idle. The interface number alone now
  decides, since no other version uses it.
- **The score splash shows again.** The first time it came up in a session it
  set its text before its font, which the game rejects ("FontString:SetText():
  Font not set"), so the splash and its Preview button never appeared. It now
  takes its font first.

### Changed
- **Caught errors say where they happened.** Some errors the game raises name
  no file or line, so `/tc diag` showed what went wrong but not where. Each
  caught error now lists the file and line in TankCompanion that made the
  failing call, and the same message from two places is kept as two entries.
- **Errors that name no file are still caught.** The game's own errors, like
  "Font not set", don't say which addon caused them, and were kept only when
  the game happened to add a "Lua Taint" note. Now the addon checks whose code
  made the failing call and keeps the error when it was TankCompanion's.
  Errors from other addons are still left alone.