…platforms

The implementations incorrectly assume there are two trailing characters to ignore for the newline (i.e. "\r\n"), which is the case for Windows, however this is only a single character on Unix platorms ("\n").
This fix uses Environment.NewLine.Length to determine how many trailing characters to ignore, depending on which platform is being used.

* FIXED: Fix issue with string builder removing too much raw sln data on Unix platforms.
             Related issue: 3F#57