cpp/experimental/fs/directory iterator/directory iterator

Constructs a new directory iterator.

@1@ Constructs the end iterator.

@2@ Constructs a directory iterator that refers to the first directory entry of a directory identified by. If refers to a non-existing file or not a directory, returns the end iterator.

Exceptions
@1@

@2@ if an error occurs. The exception object is constructed with as an argument.

@3@