Remove extra whitespaces
Restore CONS evaluation on REPL

'CL-USER> (cons 1 2)' evaluates to error, too.

JavaScript EVAL interprets curly braces of object literals as
markers of a block of code. We avoid this by wrap object literals
within a pair of parens.
Restore CONS evaluation on REPL by tweaking js-stmt

thanks to davazp
Merge pull request #153 from jnjcc/master

Restore CONS evaluation on REPL by tweaking js-stmt