Support Atmos command line

This patch makes cc65-built Atmos files look like BASIC programs (with machine language) instead of pure ML programs.  And, the tape files don't have the autostart flag turned on.  That means:

1. We finally are allowed to type command-line arguments for Atmos programs.
2. We don't need to remember an address number, in order to start an Atmos program; we just type "RUN".
> As far as I see, it's only a question of style to use `__BASHEAD_LAST__` here instead of `$050E`. In that case, I ask you to stick to `$050E`, as this is the style used in the other cfg's. See, for example, `c64.cfg`.


I think that we should go in the opposite direction; that is, we should use more symbols and expressions.

* It's more versatile.
* It would make ld65 adjust addresses and do calculations automatically, for us.  For example, if we changed the size of a BASIC header, then `RAM`'s position would be moved by ld65; we wouldn't need to think about it.
* And, it would increase the consistency of the configuration files.  For example, most of the Commodore CFG files would have the exact same memory section:

```
MEMORY {
    ZP:       file = "", define = yes, start = $0002,            size = $001A;
    LOADADDR: file = %O,               start = __RAMSTART__ - 2, size = $0002;
    HEADER:   file = %O, define = yes, start = __RAMSTART__,     size = $000D;
    RAM:      file = %O, define = yes, start = __HEADER_LAST__,  size = __RAMEND__ - __RAM_START__ - __STACKSIZE__;
}
```