Reducing memorizing start position by create nodes at the right location as much as possible.

https://code.google.com/p/esprima/issues/detail?id=530

Before:

|Source|Size|Time|
|:--:|--:|--:|
|Underscore 1.5.2|42.50|3.72|
|Backbone 1.1.0|58.70|3.98|
|MooTools 1.4.5|156.70|20.33|
|jQuery 1.9.1|262.10|21.22|
|YUI 3.12.0|330.40|21.41|
|jQuery.Mobile 1.4.2|442.20|74.48|
|Angular 1.2.5|701.70|47.83|
|Total|1,994.30|192.97|

After:

|Source|Size|Time|
|:--:|--:|--:|
|Underscore 1.5.2|42.5|3.47|
|Backbone 1.1.0|58.7|3.67|
|MooTools 1.4.5|156.7|19.76|
|jQuery 1.9.1|262.1|20.84|
|YUI 3.12.0|330.4|22.38|
|jQuery.Mobile 1.4.2|442.2|63.61|
|Angular 1.2.5|701.7|44.09|
|Total|1994.3|177.82|

Speed up: **8.49%** (1.085x)