lavapipe: minor exts
This just adds the trivial support for VK_EXT_shader_stencil_export VK_EXT_post_depth_coverage
and adds lavapipe plumbing to support VK_KHR_indirect_draw_count
This just adds the trivial support for VK_EXT_shader_stencil_export VK_EXT_post_depth_coverage
and adds lavapipe plumbing to support VK_KHR_indirect_draw_count