Backport changes from posix-paths PR:

* add isFileName
* add hasParentDir
* add hiddenFile
* add our own openFd version for more control
* small documentation improvements
* add a getDirectoryContents' version that works on Fd
* fix linting warnings
* lift version constraints in benchmark

Also adjust HPath.IO to work with the new API.

hpath.cabal

@@ -29,6 +29,7 @@ library
                      HPath.Internal,
                      System.Posix.Directory.Foreign,
                      System.Posix.Directory.Traversals,
+                     System.Posix.FD,
                      System.Posix.FilePath
   build-depends:     base >= 4.2 && <5
                    , bytestring >= 0.9.2.0
@@ -111,9 +112,9 @@ benchmark bench.hs
       bytestring,
       unix,
       directory  >= 1.1 && < 1.3,
-      filepath   >= 1.2 && < 1.4,
+      filepath   >= 1.2 && < 1.5,
       process    >= 1.0 && < 1.3,
-      criterion  >= 0.6 && < 0.9
+      criterion  >= 0.6 && < 1.2
   ghc-options: -O2
 
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