sending code from buffer to inferior mode on dotnet fsi doesn't work.

### Description

We can use dotnet fsi on the inferior mode, but we can't send any code

### Repro steps

`C-c C-r` of some code in F# buffer and use `dotnet fsi` as the toplevel to run

### Expected behavior

An inferior session with dotnet starts and the code is sent to the inferior mode

### Actual behavior

The following error is thrown:
```> Failed to install ctrl-c handler - Ctrl-C handling will not be available. Error was:
Could not load file or assembly 'Mono.Posix, Version=2.0.0.0, Culture=neutral, PublicKeyToken=0738eb9f132ed756'. The system cannot find the file specified.
System.Exception: You need to implement this function.
at .$FSI_0002.main@()
```

### Related information

* Operating system - Fedora 30
* Branch - MELPA 20190609.1317
* Emacs version 26.2
* .NET Runtime, CoreCLR or Mono Version - dotnet, F# interactive 10.6

I will be looking at doing the necessary changes to support properly dotnet fsi on fsharp-mode