Custom doesDirectoryExist API does not work with ghcjs

[dfordivam]

This unfortunately does not work correctly with ghcjs (nodejs) (The System.Directory API works fine.)

glob/System/FilePath/Glob/Utils.hs

Lines 106 to 107 in 090181e

	-- Significantly speedier than System.Directory.doesDirectoryExist.
	doesDirectoryExist :: FilePath -> IO Bool

I think it is not a critical to support ghcjs, but opening this issue in case someone hits a problem.