ref #3: apply Graham's 5.0.1C patch, 2013-09-02

From patch original header:
* patched PlacesUtils.toJSONString -> JSON.stringify
* updated version to 5.1.0C
* updates maxversion to 23.* (DL)

Patch was recreated and verified between v5.1.0B and v5.1.0C .xpi bundles
- added syncplaces-5.1.0C-sm+fx.xpi
Merge branch 'hotfix/5.1.0C'
Merge tag 'v5.1.0C' into develop

syncplaces-5.1.0C-sm+fx.xpi