crepl: update docs for eventual CREPL_UNDECLARE builtin
crepl: implement CREPL_DECLARED
crepl: always heap-allocate on 8-byte boundry
crepl: check for keyword completions last
So they can be "shadowed" by macros and stuff.
Also adds completions for printf, scanf, strfmon, and strftime, since
those are used by the gnu::format attribute.
crepl: remove brackets around noreturn completion
Since it may be completed already within brackets
crepl: complete attributes without underscores
crepl: import builtin_type & decl_storage as members
crepl: store pointer to declaration in scope
Instead of just its ID. This will allow for stuff like CREPL_DECLARED.
check: add note to opt::NO_THREADS docs
check: don't initialize static variables at runtime
check: add conversion to void for expr_kind stmts
parse: fix inexhaustive match
hacc.1: minor spelling changes
Add XXX comments about optimizing representation