es.js: fix location of one of the lines

Not really noticable...
parser: rename function parameter for clarity
parser: remove unnecessary lambda
parser: remove unused function parse_redirection_input

Apparently this was never called and already handled in parse_redirections1.
parser: add support for <& redirections
parser: don't choke on invalid use of shell redirection

Malformed commands such as 'ssh.. <user>@<pass>' would confuse the parser
because of a missing target for the last output redirection. These are quite
popular in examples, so it's unfortunate we can't display something more
meaningful than an error.

(bash errors out with a similar message to ours)