libpath.Rust - TODO

Functional improvements

The following path semantics remain implementation work and are not part of the boilerplate baseline.

Full path support (in libpath::util::windows):
- Drive-rooted paths;
- Drive-relative paths;
- Home-rooted paths;
- Slash-rooted paths;
- relative paths;
- UNC-rooted paths;
- UNC-incompleted paths;
- (some of) above with:
  - Local device prefix "\\.\";
  - Root local device prefix "\\?\";
  - Local device prefix and UNC designator "\\.\UNC\";
  - Root local device prefix and UNC designator "\\?\UNC\";
  - NT path prefix "\??\";
- Device names (such as "COM1");
- Support (sadly) full flexibility in Windows paths for mixed use of '\' and '/' (though not for runs);
- Detection of trailing space as invalid character(s);
Rename ClassificationResult to PathDescriptor;
~~~Rename ClassificationResult#Entry to #EntryName~~~ - ✅;
Remove ClassificationResult#FirstInvalid and use in function calls;
Correct handling of entry-names with trailing '.' character(s);
Add many and varied test cases with invalid characters / names;
Add trait Path that provides access to elements (as &str, etc.);
Implement IGNORE_SLASH_RUNS;
Implement IGNORE_INVALID_CHARS;
Implement RECOGNISE_TILDE_HOME;
Implement IGNORE_INVALID_CHARS_IN_LONG_PATH;
Implement path normalisation (Unix and Windows) : to_os_normal(), to_asbtract_normal();
Remove the redundant libpath::libpath:: namespace;