Why is `catch` a [reserved] keyword?

[C. Scott Ananian]

My guess would be that `catch` is reserved so that (in a future
version of JavaScript) this won't be ambiguous:
```
try { stuff(); }
catch(e1) { }
catch(e2) { }
```

Currently JS only allows a single catch clause.  But if it ever grows
guarded catch expressions, then you would want to add multiple catch
clauses.  All but the first could potentially be ambiguous with an
invocation of a function named `catch`.
  --scott