This removes the need to run c-compilation on one file, and allows us
to in future c++-ify this a bit.
There's a lot of bit-fiddling here that is quite unnecessary, better
error-handling would be nice...
So far this removes a few more unused things (because I would have had
to port them), including:
- Functions with ARITY > 3 (even 3 isn't used, but just so we don't
get complacent)
- Variables
- Most functions moved out of the header, because only te_interp is used.
- The te_print function
This now reports "TOO_MANY_ARGS" instead of no error (and triggering
an assertion).
We might want to add a new error type or report the missing operator
before, but this is okay for now.
This turns a bunch of ifs on their heads.
We often see this pattern in te:
```c
if (s->type != SOME_TYPE) {
// error handling
} else {
// normal code
}
```
Only, since we want to return the first error, we do
```c
if (s->type == SOME_TYPE) {
// normal code
} else if (s->type != TOK_ERROR) {
// Add a new error - if it already has type error
// this should already be handled.
}
```
One big issue is the comma operator, that means arity-1 functions can
take an arbitrary number of arguments. E.g.
```fish
math "sin(5,9)"
```
will return the value of sin for _9_, since this is read as "5 COMMA
9".
