Changes

;Stability: Fx20 is more stable than previous release. We dropped [https://crash-stats.mozilla.com/daily?p=FennecAndroid&v[]= below 2%]. We have also been landing some fixes that might affect the SQL related crashes. We found some explicit problems in the code thanks to the "Dump all threads" feature in our test framework and the ANR work Jim has been adding. Nightly has no SQL DB locking crashes since Apr 6 builds. Let's keep our fingers crossed!