add OP_REST for rest arguments

bump stack height (just in case)

pp->print & better vararg support for builtin functions

fix how arguments are evaluated before funcall the args are a linked list, not an array!

better pretty-print for funcalls

create correct string literals

fix val_eq for casted integer

handle numbers and casts better now u8, u16 and u32 are stored in a respective field in the struct and "untagged" numbers are a plain int64_t.

lowercase cast error messages

fix casting check: 255 is a valid u8!

fix the casting in global_set

allow casts in global vars

drop builtin dummy, add pp and skip

set argc on builtins

change how nativefns are called nativefn (aka built-ins) now gets their arguments on the stack, while script procedures still gets them as variables.