Changelog for filepath-1.4.2

Changelog for `filepath` package

Note: below all FilePath values are unquoted, so \\ really means two backslashes.

Bundled with GHC 8.0.1
Add replaceExtensions and stripExtension functions.
Make isValid detect more invalid Windows paths, e.g. nul .txt and foo\nbar.
Improve the documentation.
Bug fix: isValid "\0" now returns False, instead of True

Bundled with GHC 7.10.1
New function: Add -<.> as an alias for replaceExtension.
Semantic change: joinDrive /foo bar now returns /foo/bar, instead of /foobar
Semantic change: on Windows, splitSearchPath File1;\"File 2\" now returns [File1,File2] instead of [File1,\"File2\"]
Bug fix: on Posix systems, normalise //home now returns /home, instead of //home
Bug fix: normalise /./ now returns / on Posix and \ on Windows, instead of // and \\
Bug fix: isDrive "" now returns False, instead of True
Bug fix: on Windows, dropTrailingPathSeparator / now returns / unchanged, instead of the normalised \
Bug fix: on Windows, equalFilePath C:\ C: now returns False, instead of True
Bug fix: on Windows, isValid \\\foo now returns False, instead of True
Bug fix: on Windows, isValid \\?\D:file now returns False, instead of True
Bug fix: on Windows, normalise \ now returns \ unchanged, instead of \\
Bug fix: on Windows, normalise C:.\ now returns C:, instead of C:\\
Bug fix: on Windows, normalise //server/test now returns \\server\test, instead of //server/test unchanged
Bug fix: on Windows, makeRelative / // now returns //, instead of ""