new optimizer command: staticize non-virtual instance method

I added yet another optimizer command to JSX, which staticize non-virtual methods and eliminate runtime method lookup. We might change the name of this command because "staticize" is not very descriptive. Below are scores I measured with wasabiz/jsx-v8bench. The difference between them is apparently slight but I think this is enough good to merge.

before
```
Richards: 6397
DeltaBlue: 9045
Crypto: 7138
RayTrace: 12641
RegExp: 1664
Splay: 2181
NavierStokes: 10694
----
Score (version 7): 5729
```

after
```
Richards: 6241
DeltaBlue: 9481
Crypto: 7495
RayTrace: 14004
RegExp: 1668
Splay: 2646
NavierStokes: 9844
----
Score (version 7): 5968
```