* Removed ToJSVal<jsval> because it's treated as ToJSVal<long> and
causes minor confusion and/or compiler errors.
Changed script interface functions to return either C++ types or a
jsval_t wrapper.
* Replaced some C casts with static_cast to avoid significant confusion
and to cause compiler errors instead.
* Removed some redundant argument-checking code. Simplified some
string-generating code.
* Fixed some "dereferencing type-punned pointer will break
strict-aliasing rules" warnings (from `g++ -O3`).
This was SVN commit r5115.
Entities will now leave all their auras and cancel all their productions
when they change ownership, which will be useful when we have
convertible buildings.
This was SVN commit r4156.
