R8format

- Fixed: `RomImage.patches()` now works if more than one patchspec matches.
- Fixed: `RomImage` now considers `C:…` to be a path instead of a URL,
for compatibility with Windows file paths.
- Test framework: `Test` accepts `-c` as well as `-C` to do clean build.

- Added: A `binary.romimage.RomImage` can now be cleared (set to length 0)
with loadspec of `--`. This is useful to "disable" a default RomImage.
- Fixed: `binary.romimage` no longer catches `HTTPError` where it tried
(but failed) to print a message and exit.

- Added: `binary.romimage`, a package to download/build/patch ROM images.
- Changed: `binary.tool.asl` produces better messages when failing to parse
symbol values in ASL listing/map files. (This better exposes an ASL bug.)

- (Not released)

- Added: missing `pytest_pt` top-level module now present.
(t8dev and other repos using their own copy now no longer need to do so.)

- Initial release.



<!-------------------------------------------------------------------->
[ISO dates]: https://xkcd.com/1179/
[cynic-net/pypi-release]: https://github.com/cynic-net/pypi-release
[keepachangelog.com]: https://keepachangelog.com/
[pyver]: https://packaging.python.org/en/latest/specifications/version-specifiers/#version-specifiers
[semver]: https://en.wikipedia.org/wiki/Software_versioning#Semantic_versioning