Add missing capability when QueueFamily scope is used

Also, if this capability is added and the memory model is not
otherwise enabled by pragma, enable it as part of postprocessing.

Test/spv.queueFamilyScope.comp

@@ -0,0 +1,10 @@
+#version 450
+#extension GL_KHR_memory_scope_semantics : require
+
+layout (binding = 0) buffer Buffer { uint a; } A;
+
+void main()
+{
+    atomicLoad(A.a, gl_ScopeQueueFamily, gl_StorageSemanticsBuffer, gl_SemanticsAcquire);
+}
+