`lwd=2` in `plot.xts`

```
par(lwd=3)
quantmod::getSymbols('PSAVERT', src='FRED')
plot.xts(PSAVERT)
```

On line 10 of `grep(body(plot.xts), patttern="lwd")` , `lwd` is being passed to `axis` and `ann`.

I'll submit a patch to fix this, except I don't know what the new method (¿`@chob`'s?) for hiding the word `lwd` for multiple namespaces.

Same problem if you `plot.xts( PSAVERT, lwd=3)`.
