Update C# bindings to work with SWIG 3.x

[geographika]

See #5575

This initial pull request brings the number of errors when building with SWIG 3.0.12 from 1592 Error(s) to8 Error(s).

The remaining errors are:

[00:02:38]   mapscript.cs(25,58): error CS0234: The type or namespace name 'EntryPoint' does not exist in the namespace 'System.Runtime.InteropServices' (are you missing an assembly reference?) [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]
[00:02:38]   mapscript.cs(25,4): error CS1729: 'DllImportAttribute' does not contain a constructor that takes 2 arguments [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]
[00:02:38]   mapscriptPINVOKE.cs(191,10): error CS0111: Type 'mapscriptPINVOKE' already defines a member called '.cctor' with the same parameter types [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]
[00:02:38]   mapscriptPINVOKE.cs(313,3): error CS0246: The type or namespace name 'ThreadStaticAttribute' could not be found (are you missing a using directive or an assembly reference?) [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]
[00:02:38]   mapscriptPINVOKE.cs(313,3): error CS0246: The type or namespace name 'ThreadStatic' could not be found (are you missing a using directive or an assembly reference?) [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]
[00:02:38]   mapscriptPINVOKE.cs(298,58): error CS0234: The type or namespace name 'EntryPoint' does not exist in the namespace 'System.Runtime.InteropServices' (are you missing an assembly reference?) [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]
[00:02:38]   mapscriptPINVOKE.cs(298,4): error CS1729: 'DllImportAttribute' does not contain a constructor that takes 2 arguments [C:\projects\mapserver\build\mapscript\csharp\mapscript.vcxproj]

[sdlime]

@geographika - have you had chance to investigate the AppVeyor issues? I assume that's more relevant to this particular issue. --Steve

[geographika]

@sdlime - the issues relate to using the newer version of SWIG rather than Appveyor, so the C# interface files need changes. I've not yet been able to fix the remaining 8 issues but will have another look.

Travis is passing as the C# bindings aren't built on Linux.

[geographika]

Related pull request in GDAL: OSGeo/gdal#824

[geographika]

This pull request is now complete. It does the following:

• Replaces SWIG 1.3.39 used in the GISInternals Buildkit in Appveyor with the latest version of SWIG 3.0.12
• This is then used to build the .NET MapScript and Python MapScript

SWIG 1.3.39 was released in 2009 and has issues with generating Python3 MapScript (and possibly PHP).

Nearly all changes to the CSharp MapScript interface files are to fully qualify .NET types. This is due to the following:

SWIG 3 fully qualifies the use of all .NET types. Furthermore, SWIG 3 avoids using directives in generated code. This breaks backwards compatibility with typemaps, pragmas,
etc written for use with SWIG 2 that assume the presence of using System; or using System.Runtime.InteropServices

http://www.swig.org/Doc3.0/CSharp.html#CSharp_introduction_swig2_compatibility

Only after completing the majority of these changes did I discover there is a flag to ignore these and maintain backwards compatibility:

If SWIG2_CSHARP is defined, SWIG 3 generates using directives in the intermediate class, module class, and proxy class code similar to those generated by SWIG 2.

By this stage it was as easy to complete the changes, which may make the code more future proof. .NET MapScript still compiles with SWIG 1.3.39 even with the changes in this pull request.

One further issue was the following needed to be commented out:

%pragma(csharp) imclasscode=%{
  static $imclassname() {	  //static $imclassname() {
  }	  //}

Otherwise the following build error occurred:

 mapscriptPINVOKE.cs(191,10): error CS0111: Type 'mapscriptPINVOKE' already defines a member called '.cctor' with the same parameter types [C:\Installation\release-1911-x64-dev\build\mapscript\csharp\mapscript.vcxproj]