appmake +zx: add generation of 48k/128k .sna snapshots

[aralbrec]

Some tools are beginning to appear for the ZX Next machine that are using .sna snapshots for shortcuts. Add this capability to appmake to take advantage of that, maybe look at the .z80 format too.

A particular test case is CSpect that will take 48k .sna with symbol data to implement a debugger.

I don't load 128K SNA files - I did start adding it, but realised I didn't need it. As I said before, with the SD card being so simple to load from (see included source), you can easily put all data on the SD card and just have the 48K for code - especially for testing just now.

Symbol format is very simple

00000 LABEL
00000 LABEL@LOCAL

so one label per line, hex value first then label. Local labels if saved out can be passed in as above, and the debugger will strip the LABEL part of it.

[aralbrec]

Adding "--sna" to an "appmake +zx" invoke will cause the generation of a .sna snapshot file instead of a .tap file.

The .sna snapshot will automatically be either the 48k or the 128k type depending on whether the 128's extra memory banks are involved in the compile.

For typical compile lines for the zx, adding -Cz"--sna" will cause a snapshot to be generated.