[spod] Add TType sys.db.SNull case check

[waneck]

Okay So this gets it to compile on the Haxe side on Java/C#. But some strange things happen

For example, Issue3031's -D dump looks like this:

    testArty(method) : Void -> Void

     = [Function:Void -> Void]
        [Block:Void]
            [Var a(31461):String] [Const "":String]
            [Block:Unknown<692>]
                [Var _g(31462):StringBuf] [New:StringBuf] StringBuf
                [Block:Unknown<692>]
                    [Var notNull(31464):StringBuf] [Local _g(31462):StringBuf]
                    [If:String]
                        [Parenthesis:Bool]
                            [Binop:Bool]
                                [Local _g(31462):StringBuf]
                                ==
                                [Const null:Null<Int>]
                        [Then:String] [Binop:String]
                            [Local a(31461):String]
                            =
                            [Const "null":String]
                        [Else:Unknown<691>] [Switch:Unknown<691>]
                            [Parenthesis:StringBuf] [Local _g(31462):StringBuf]
                            [Default:String]
                                [Binop:String]
                                    [Local a(31461):String]
                                    =
                                    [Const "not null":String]
            [Call:Void]
                [Field:v : String -> v2 : String -> ?pos : Null<haxe.PosInfos> -> Void]
                    [Const this:unit.issues.Issue3031]
                    [FInstance:v : String -> v2 : String -> ?pos : Null<haxe.PosInfos> -> Void]
                        unit.Test
                        eq
                [Const "not null":String]
                [Local a(31461):String]
                [ObjectDecl:{ methodName : String, lineNumber : Int, fileName : String, className : String }]
                    fileName: [Const "Issue3031.hx":String]
                    lineNumber: [Const 17:Int]
                    className: [Const "unit.issues.Issue3031":String]
                    methodName: [Const "testArty":String]

Look specially at this:

                    [If:String]
                        [Parenthesis:Bool]
                            [Binop:Bool]
                                [Local _g(31462):StringBuf]
                                ==
                                [Const null:Null<Int>]

It's comparing a StringBuf to a Null<Int>

[Simn]

Yeah there was a really weird null-wrapping logic in the pattern matcher. I kept it for now because I don't remember why I made it like that.

I've also fixed an issue with the Normalize filter and now things compile. The only failing tests are related to overloads:

TestOverloads.hx:33: Int,Dynamic,String should be Null<Int>,Dynamic,Bool
TestOverloads.hx:35: Int,Dynamic,String should be Null<Int>,Dynamic,Bool
TestOverloads.hx:49: Int,Dynamic,String should be Null<Int>,Dynamic,Bool
TestOverloads.hx:50: Int,Dynamic,String should be Null<Int>,Dynamic,Bool

I'll let you deal with that.