mono/mono — pull request #1466 by schani (2014-12-19 01:11:55+00:00)
Title: Stage unified card table scanning

This is a performance win, as well as a simplification. Performance results (20 runs each):

![sgen-unified-card-table-scanning](https://cloud.githubusercontent.com/assets/61363/5498739/74f122e6-86d8-11e4-90e7-34db59cd92e5.png)