vg_load_svg: Add Mask, ClipPath nodees as dummy.

vg_load_svg: Add Mask, ClipPath nodees as dummy.

Summary:
Mask and clippath TAG are not supported yet.
If this TAG is used, the Child TAG declared with this TAG may cause problems.
To prevent that, declare them as Unknown types until they are supported. (display=none)

Test Plan: N/A

Reviewers: Hermet, smohanty

Reviewed By: Hermet

Subscribers: cedric, herb, #reviewers, kimcinoo, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D12139

Change-Id: I007c4538d9b2ab92b6b58e954215c63a23541d18