Add locations to opaque types for OpenGL

Test/baseResults/spv.debugInfo.1.1.frag.out

@@ -94,6 +94,7 @@ void main()
                               MemberDecorate 54(ubuf) 0 Offset 0
                               Decorate 54(ubuf) Block
                               Decorate 56 DescriptorSet 3
+                              Decorate 69(s2d) Location 0
                               Decorate 69(s2d) DescriptorSet 3
                3:             TypeVoid
                4:             TypeFunction 3

Test/baseResults/spv.debugInfo.frag.out

@@ -97,6 +97,7 @@ void main()
                               Decorate 54(ubuf) Block
                               Decorate 56 DescriptorSet 3
                               Decorate 56 Binding 0
+                              Decorate 69(s2d) Location 0
                               Decorate 69(s2d) DescriptorSet 3
                               Decorate 69(s2d) Binding 1
                3:             TypeVoid

glslang/MachineIndependent/iomapper.cpp

@@ -431,7 +431,8 @@ struct TDefaultIoResolverBase : public glslang::TIoMapResolver
 
         // no locations added if already present, a built-in variable, a block, or an opaque
         if (type.getQualifier().hasLocation() || type.isBuiltIn() ||
-            type.getBasicType() == EbtBlock || type.containsOpaque())
+            type.getBasicType() == EbtBlock ||
+            (type.containsOpaque() && intermediate.getSpv().openGl == 0))
             return -1;
 
         // no locations on blocks of built-in variables