Issue with Sprite created from SVGs which contain <defs>

[soumen-basak]

In the default mode SVGs which contain and are referenced with their ids (example below) are not able to access the in the sprite. This is because they are concatenated in their respective

Example sprite (with issue):

<svg>
  <svg>
    <defs>
    </defs>
    ...
  </svg>
  <svg> ...
  </svg>
  ...
</svg>

Example sprite (how it should be):

<svg>
  <defs>
  </defs>
  <svg> ...
  </svg>
  <svg> ...
  </svg>
  ...
</svg>

[soumen-basak]

Upon more examination it seems problem is of duplicate ids being present in the sprite. The original ids are being replaced by 'a', 'b' and so on. With the next svg file being processed this is reset and again the ids start from "a'. This creates duplicate ids in the sprite Seems this is the same problem as #108