Changed builtin keywords in the script engine to case sensitive.

- Any scripts using the wrong case, that were throwing deprecation
  warnings until now, will become invalid.
- Related to bugreport:7810.

Signed-off-by: Haru <haru@dotalux.com>
Changed variables, labels, functions, commands to case sensitive.

- Fixes bugreport:7810, thanks to Wend, kyeme, evilpuncker, jaBote, and
  various other people I may be forgetting to mention
  http://hercules.ws/board/tracker/issue-7810-disguise-script-command
- Due to the nature of this change, I'm leaving the deprecation messages
  lingering around for a while more (as errors rather than warnings), to
  make sure they won't pass unnoticed, in case you haven't yet updated
  your custom scripts to comply with this.
- Special thanks to Ind.

Signed-off-by: Haru <haru@dotalux.com>
Changed item Aegis ID and mob Sprite ID lookups to case sensitive.

Signed-off-by: Haru <haru@dotalux.com>