SPV: Correctly enforce 'location' presence on in/out blocks.

Blocks have this on members, not the object.

Test/spv.noLocation.vert

@@ -8,6 +8,25 @@ layout(location = 1) out vec4 out1;
 out vec4 out2;
 layout(location = 3) out vec4 out3;
 
+layout(location = 10) out inb1 { 
+    vec4 a;
+    vec4 b;
+} inbi1;
+out inb2 { 
+    layout(location = 12) vec4 a;
+    layout(location = 13) vec4 b;
+} inbi2;
+out inb3 {
+    vec4 a;
+    vec4 b;
+} inbi3;
+
+layout(location = 14) out struct S1 { vec4 a; } s1;
+out struct S2 { vec4 a; } s2;
+
+struct SS { int a; };
+out layout(location = 15) SS ss1;
+out SS ss2;
 
 void main()
 {