romload.cpp: reduce copy-pasta (nw)
(nw) I fixed the errors found by adding validation to software list data areas.
Most of them seem to be simple copy-paste errors hidden by the fact that the
default device_image_interface loader ignores the data area size (as opposed to
the "ROM" loader). There was one C64 cartridge with a missing zero on the data
area size that was pretty clearly wrong.
Get rid of a couple of copies of the CC0 text. Add header comment to
CC0 files to remind people editing them what the terms are. Also add
some missing XML headers. The header comments in layouts won't bloat
the binary - they get stripped out before compressing, same as any other
comments.
