add "tostring" to real type
## Summary
<!-- Summarize the wanted feature concisely -->
numerical types "double/integer/.." have "tostring" helper, but "real" type no. It should be better add "tostring" also for "real" Type
## System Information
<!-- Provide details if the feature request is only valid for specific platforms, otherwise remove this section -->
- win 10-pro
- x86_64
- PC
## Example Project
<!-- If possible, please create an example project that shows the usage of the wanted feature and the advantage of it, and link to it here in the bug report. -->
```pascal
procedure TForm1.Button1Click(Sender: TObject);
var
a : double;
b : integer;
c : real;
s : string;
begin
s:=a.tostring;
s:=b.tostring;
s:=c.tostring; <-- this line does not complie, Error:illegal qualifier
end;
```
## Relevant 3rd party information
<!-- If this feature is already available in other languages please provide some information about it or link to Delphi Documentation if it's about Delphi compatibility -->
issue