sokol: update sokol_gfx.h to the LAST version, and fix example 06 (#13100)

vlib/sokol/gfx/enums.v

@@ -297,3 +297,10 @@ pub enum Action {
 	dontcare
 	_num
 }
+
+pub enum UniformLayout {
+	uniformlayout_default = 0 // value 0 reserved for default-init
+	uniformlayout_native // default: layout depends on currently active backend
+	uniformlayout_std140 // std140: memory layout according to std140
+	_num
+}

vlib/sokol/gfx/gfx_structs.c.v

@@ -260,6 +260,7 @@ pub fn (mut desc ShaderStageDesc) set_image(index int, name string) ShaderStageD
 struct C.sg_shader_uniform_block_desc {
 pub mut:
 	size     usize
+	layout   UniformLayout
 	uniforms [16]ShaderUniformDesc
 }