+0/-0 not distinguished

[IgnoredAmbience]

OCaml's compare function as used in JsInterpreterExtraction.v#JsNumber.number_comparable does not distinguish +0 and -0 as number_comparable requires.
number_comparable is used in several places for the explicit +0 -0 tests, in particular the SameValue algorithm.

The following test cases are probably failing in part due to this:

• 15.2.3.6-4-64.js
• 15.2.3.6-4-65.js
• 15.2.3.6-4-86.js
• 15.2.3.6-4-87.js
• 15.2.3.6-4-218.js
• 15.2.3.6-4-219.js
• 15.2.3.6-4-246.js
• 15.2.3.6-4-247.js

(This issue is fixed in jsexplain)