Readonly should only apply to default buffers

Ref #1298

internal/buffer/buffer.go

@@ -211,7 +211,7 @@ func NewBuffer(r io.Reader, size int64, path string, startcursor Loc, btype BufT
 		b.EventHandler = NewEventHandler(b.SharedBuffer, b.cursors)
 	}
 
-	if b.Settings["readonly"].(bool) {
+	if b.Settings["readonly"].(bool) && b.Type == BTDefault {
 		b.Type.Readonly = true
 	}
 

internal/buffer/settings.go

@@ -35,7 +35,7 @@ func (b *Buffer) SetOptionNative(option string, nativeValue interface{}) error {
 		}
 	} else if option == "encoding" {
 		b.isModified = true
-	} else if option == "readonly" {
+	} else if option == "readonly" && b.Type == BTDefault {
 		b.Type.Readonly = nativeValue.(bool)
 	}