debugignore: eliminate inconsistencies with `hg status` (issue5222) Using a matcher for this command allows processing the named file(s) as relative to cwd. It also leverages the icasefs normalization logic the same way the status command does. (However, a false indicator is given for a nonexistent file in some cases, e.g. passing 'foo.REJ' when that file doesn't exist, and the rule is '*.rej'. Maybe the regex itself needs to be case insensitive on these platforms, at least for the debug command.) Finally, the file printed is relative to cwd and uses platform specific slashes, so a few (glob)s were needed in seemingly unrelated tests.