The patch adds a new icon called ICON_FILE_SVG in the icons sheet, in order to use it in the file browser in place of the generic ICON_FILE_3D, used for other IO file types.
The new FILE_TYPE_SVG is also used to properly filter SVG files in the grease pencil Import SVG operator (also removed the ot->check function there, as far as I understand, it wasn't needed).

