Bug 905135 - move zero values to their point of use in nsSMILCSSValueType.cpp; r=dholbert
Bug 903543 - eliminate static constructors for SMIL type singletons; r=dholbert

Add MOZ_CONSTEXPR to the constructors to inform the compiler the constructors
can be folded away.  Remove protected/private destructors so that static
destructors don't have to be registered with static constructors.
Bug 905149 - make mozilla::CallStack constexpr to avoid static constructors; r=ehsan