Fix PR35078 - recursive directory iterator's increment method throws incorrectly.

The guts of the increment method for recursive_directory_iterator
was failing to pass an error code object to calls to status/symlink_status,
which can throw under certain conditions.

This patch fixes the issues by correctly propagating the error codes.
However the noexcept still needs to be removed from the signature, as
mentioned in LWG 3014, but that change will be made in a separate commit.

llvm-svn: 316939