* src: support for serializing more compiler values

* initial work on __toglobal protocol

* gen_c: serialize basic compiler symbols, builtins and types
* store only anchor/stack trace for origin, not entire value

* Boxed, ConstPtr are no longer of reference type

* expander: fixed dispatch

* converted expander class to context struct

* restricted Scope keys to Symbol type again

* prevent building aggregates of global references

* SCOPES_CORE_PATH env allows to change path to core module

* "finally" clauses of try blocks behave like conditional labels, turning void if any merge source is void
* new env options to facilitate halting on a particular error instance

* src: improve auto-capturing of values

* src: removed explicit ctx argument from most builder functions

* improved native closure interface
* initial quoted flow

* renamed TypedValue -> Value

* removed UntypedValue and all associated API functions

* expander is almost fully translated, except for quotes

* initial work on generating typed IR directly in expander

* removed `sc_typify_template` (is now an inline macro)
* expand produces a closure rather than a template
* `sc_closure_new` allows passing of empty env value

* closure handlers are function pointers directly

* fixed find_elongations()