Reduce initial allocation to 1 MB now that it can by increased at runtime.
Also remove 'noreturn' attribute from the public API.
If out_of_memory() returns, GC will abort() internally.
Fix tree_replace() to handle recursive data structures.
Fix some other minor bugs in the reader and interpreter.
Implement comment-escapes in the string parser, for more readable input.
Allow input program files (*.rla) to be invoked directly, with arguments.
Add a simple string->number converter as a builtin function.
Also refactored some GC code into smaller functions.
Weak boxes and wills will be useful for implementing weak hash tables,
which in turn will be used to store dynamic parameters efficiently.
Jesse D. McDonald