The & prefix on editor option does not work properly when a file has errors

I've just got set up with the Haskell Platform again after a major crash, and installed the new one with GHC 8.0. I'm using Windows 10.

As usual, I've set my editor option to `&gvim`, so that I can just fire up the editor from inside WinGHCi but still not lock up the latter. However, this no longer works when a file contains errors at startup. I usually try not to leave files around with errors in them, but GHC sometimes gets stricter. My dabbling-around file `C.hs` started with `module Main where` but had no actual `main`, which is now an error:

```
Prelude> :l C
[1 of 2] Compiling Basic ( Basic.hs, interpreted )
[2 of 2] Compiling Main ( C.hs, interpreted )

C.hs:1:1: error:
The IO action ‘main’ is not defined in module ‘Main’
Failed, modules loaded: Basic.
*Basic> :e
```

After this, GVIM opens, but the file name is the incorrect `C.hs +1`.

From what I can see, the problem is with the `StartProcess.exe` helper program which WinGHCi uses for the `&` prefix: It doesn't understand GHCi `:e`'s `+linenumber` option and passes it on as part of the filename argument.

Using just `gvim` as the option works, but locks up WinGHCi.

(Well, that's with GVIM, which understands the `+1` option itself. Notepad isn't that lucky, as I accidentally discovered while testing with plain GHCi on the command line.
I didn't see any option to disable passing line numbers from GHCi, which might be considered a bug in that.)