RFA: #line directives in generated files to aid debugging

[Ben Elliston]

> The generator programs (e.g. build/genattrtab) output #line
> directives before code which has been copied from the machine
> description files, so the debugger will show you the correct
> file. But this then causes trouble when single stepping through code
> which wasn't included from the .md files.

Thanks for fixing this up; it is a right pain.

> The problem is that line numbers larger than 32767 are only
> supported with C99 or better, which we don't request from
> gcc. Because of -pedantic, GCC complains. Suggestions are welcome.

How often does it occur in practice?  How about just skipping those
#line directives when the line number is too large?  At least we could
get improved debugging in some, if not all, cases.

Ben