C++: Get rid of 'UseImpl' in TSsaDefOrUse so that it now only contains definitions.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll

@@ -1190,11 +1190,11 @@ class UninitializedNode extends Node {
   LocalVariable v;
 
   UninitializedNode() {
-    exists(Ssa::Def def |
+    exists(Ssa::Def def, Ssa::SourceVariable sv |
       def.getIndirectionIndex() = 0 and
       def.getValue().asInstruction() instanceof UninitializedInstruction and
-      Ssa::nodeToDefOrUse(this, def, _) and
-      v = def.getSourceVariable().getBaseVariable().(Ssa::BaseIRVariable).getIRVariable().getAst()
+      Ssa::defToNode(this, def, sv, _, _, _) and
+      v = sv.getBaseVariable().(Ssa::BaseIRVariable).getIRVariable().getAst()
     )
   }