Rune - Stabilization (constructors, destructors), misc.

Rune - Stabilization (constructors, destructors), misc.

* Stabilize the constructor and destructor call algorithm and fix a bug
  where we were improperly diving SCOPE_LVALUE declarations.  Mostly
  in GenCallContentGroup() and RunCallContentGroup().

* Fix bugs in the Gen*ContentGroup() that was not handling SCOPE_UNLOCKED
  properly.  Document the cases to reduce future confusion (this is complex
  stuff).

* Fix missing BEStackData in GeneratePushTmpDefaultContext().

* Run constructors after sub-constructors, run destructors before
  sub-destructors.

* Clarify how partial assignments (e.g. Fubar futz = (x:23); ) are handled
  verses complete replacements.  Constructors are still run for partial
  initializations, whereas with a complete replacement constructors on the
  target should not be run because they've already been run on the source.

* No longer run constructors on persist mappings that have already been
  initialized.  This is for consistency but also because trying to separate
  out the constructor and type-default initialization to handle the case
  I originally desired got too messy.

* Fix a bug in the resolver where declarations were being added to the
  various SemGroup->sg_*Base lists too late, preventing important type
  flags from getting set in certain reentrant situations.

* Move libdthread/refstor.c to libruntime which is where it really belongs.

* Start fleshing out and documenting the core class hierarchy.

* Continue to flesh out stdio, including full duplex streaming support.