Update error format for readability. Add spacing header<->snippet and another line between errors

Author: Jonathan Turner

src/libsyntax/errors/emitter.rs

@@ -238,7 +238,7 @@ impl EmitterWriter {
                 self.first = false;
             } else {
                 if !self.old_school {
-                    write!(self.dst, "\n")?;
+                    write!(self.dst, "\n\n")?;
                 }
             }
         }

src/libsyntax/errors/snippet/mod.rs

@@ -478,6 +478,13 @@ impl FileInfo {
                         }],
                         kind: RenderedLineKind::PrimaryFileName,
                     });
+                    output.push(RenderedLine {
+                        text: vec![StyledString {
+                            text: "".to_string(),
+                            style: Style::FileNameStyle,
+                        }],
+                        kind: RenderedLineKind::Annotations,
+                    });
                 }
                 None => {
                     output.push(RenderedLine {