Add gl4 depends to a few gl4 widgets.

[saurtron]

Work done

• Add gl4 depends to a few gl4 widgets:
  • api_unit_tracker_gl4.lua
  • gfx_deferred_rendering_GL4.lua
  • gfx_ssao.lua
  • gfx_unit_stencil_gl4.lua
  • gui_defenserange_gl4.lua
  • gui_ground_ao_plates_gl4.lua

Remarks

• Technically some of these widgets might not need the full gl4 'depends' spec (gl4 == shaders + fbo, see here).
• I think it's fine just testing for this atm, but maybe @Beherith can confirm this is fine or better be less strict (ie, just make them depend on 'shaders'). For what I seen usually this kind of widgets just checking if gl.CreateShader is available, but they also usually use more features than that, like vbos and in some cases fbos.
  • note atm I think we can't check for vbo through Platform so can't add a depends for that.
• I'm doing these ones since it's the ones failing with headless atm, in preparation for the automatic tests.
  • In the close future I intend to add to all widgets requiring it and remove ad-hoc tests, but it's quite a few of them.

[Beherith]

GL4 is completely hard required for BAR to the best of my knowledge.

[Beherith]

Even the most basic things like healthbars break without GL4 (because we use shader storage buffer objects), so minimum 4.3.