Compiler: updated dangling else check used when writing JavaScript code
Compiler: optimize conversion of constant strings to JavaScript
Compiler: improved some error messages
Compiler: leave EStr(_,`Bytes) unescaped
CLEAN
COMPILER: reenable some static eval
Merge branch 'master' of https://github.com/ocsigen/js_of_ocaml
Removed invalid optimization

"let x = 0. /. 0. in x = x" evaluates to false!
Removed caml_js_string optimization from Eval (now in Specialize_js).

That seems to be a better place: it makes sense to always perform this
optimization.
Also, the optimization was incorrect when the string contained non-ASCII
characters.