1. Always cache calls to getTypeOfSymbol, even in the error case.
2. JS expando types are now cached on the original symbol as well as the
cloned symbol. Previously they were only cached on the cloned symbol.
3. Large callees of getTypeOfSymbol (variable/param/property,
func/class/enum/module, and accessors) now handle only caching and
delegate to -Worker functions whose return values are cached
unconditionally (unlike previously).

Previously, successfully obtaining a type from a js special property
declaration would forget to pop the circularity detection stack and
check its value.