Revert "Revert "GL_ext_vulkan_glsl_relaxed extension support, and cross stage aware IO mapper""

Test/iomap.crossStage.vk.vert

@@ -0,0 +1,32 @@
+#version 460
+
+out vec4 vgo1; // declaration order different than fragment shader
+out vec2 vgo2; // declaration order different than fragment shader
+
+layout(location = 5) out outBlock {
+    vec4 o3;
+};
+
+layout (binding = 0) uniform sampler2D glass;
+
+uniform crossStageBlock1 {
+    uniform vec4 a;
+    vec4 b;
+};
+
+readonly buffer vertOnlyBlock {
+    vec2 vb1;
+};
+
+uniform crossStageBlock2 {
+    uniform vec4 a;
+    vec2 b;
+} blockName1 [2]; // instance name different from frag
+
+void main()
+{
+    vgo1 = vec4(0);
+    vgo2 = vec2(0);
+    o3 = vec4(0);
+}
+