Update spidermonkey

An issue in SpiderMonkey prevented me from running the `test262` suite: the output of `JSON.stringify` just stopped on some unicode characters (which the JSON parser complained about):
```
vlorentz@gommier:~/js/LambdaS5/tests$ cat /tmp/bar.js 
var hanidec_numbers = "〇一二三四五六七八九";
vlorentz@gommier:~/js/LambdaS5/tests$ ../bin/js -e "print(JSON.stringify(Reflect.parse(read('/tmp/bar.js'))))"
{"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":35},"source":null},"type":"Program","body":[{"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":34},"source":null},"type":"VariableDeclaration","kind":"var","declarations":[{"loc":{"start":{"line":1,"column":4},"end":{"line":1,"column":34},"source":null},"type":"VariableDeclarator","id":{"loc":{"start":{"line":1,"column":4},"end":{"line":1,"column":34},"source":null},"type":"Identifier","name":"hanidec_numbers"},"init":{"loc":{"start":{"line":1,"column":22},"end":{"line":1,"column":34},"source":null},"type":"Literal","value":"
vlorentz@gommier:~/js/LambdaS5/tests$ ../bin/js --help
Usage: ../bin/js [options] [[script] scriptArgs*]

  The SpiderMonkey shell provides a command line interface to the 
  JavaScript engine. Code and file options provided via the command 
  line are run left to right. If provided, the optional script argument 
  is run after all options have been processed. Just-In-Time 
  compilation modes may be enabled via command line options.

Version: JavaScript-C 1.8.5+ 2011-04-16
[…]
```

This bug has been fixed in the current version of SpiderMonkey. I also had to update a part of of `js/spiderMonkey.ml` as SpiderMonkey now supports only one handler in `try…catch` blocks.

I also updated the symlink `bin/js` to the newest x86_64 version (the i686 version no longer works on x86_64 architecture because of .so handling)



(PS: For some reason, GitHub wants to merge the commit `Fix test case tests/unit-tests/regexp-exec.js`, while you already merged it)