Only one file belonging to fish-shell had DOS/bogus line endings,
with `git add' picking up changes after updating .gitattributes:
hostname.fish.
Unsurprisingly, it has code to support cygwin and was likely
worked on by a user on a Windows machine. This will help
such cases in the future.
Also, in pcre2-10.21/, there was RunTest.bat which was (correctly)
CRLF formatted. We don't use this batch script at all, so rather
than LF it or add an exception, blast it away like the other pcre2
files omitted from the repo.
GitHub apparently classifies `fish-shell` as a C project because we just
barely have more C than C++ due to vendoring pcre2. Update
.gitattributes for this. Also tell it about our documentation.
see https://github.com/github/linguist
