C# project files update

- Update project files to use Visual Studio 2005 (minimum supported .NET
  is now 2.0 which is what VS 2005 supports).
- Add project files for arrays example (requires /unsafe)
- Fix support so that the project files work straight out the box on 64
  bit systems (32 bit compile is the default).
- Fix support for 64 bit builds - use the x64 platform.