Grammar gains: array types, directive flags, declaration-level directive
modifiers, parameter markers, backticked declaration names, notes after a
block-valued declaration, 'if cond then stmt', 'ifx c else v', '#module_parameters'
two-group form, '(.*)' prefix dereference, and '#asm' bodies consumed opaquely
(they are x86-64 assembly, not Jai).
Return items no longer take a default value: allowing one made
'f: (K) -> u32 = null' swallow the enclosing parameter's default and read the
rest of the parameter list as extra return values.
840a503e40