Implemented async methods in System.Data.Common
Merge pull request #628 from pdonald/master

Implemented async methods in System.Data.Common
Add facade assemblies to the rpm spec file.
Implement division/remainder in hardware when using armv7s+llvm+thumb.
Hardcode the use of  CFNetwork.GetDefaultProxy for iOS so WebProxy is not required (and can be removed by the linker)
Fix build for mobile (ios and android) wrt recent pull request on System.Data