Wrap Java's instantiation in a module since it's in the top-level scope

Unlike other languages, Java exported 'ViewCfgQuery' in top-level of the default import (java.qll).

But after the rename to ViewGraphQuery the name is too ambiguous. We can't make an alias for a parameterised module, so instead wrapping it in a module named 'PrintCfg'.

Author: asgerf

java/ql/lib/printCfg.ql

@@ -8,6 +8,7 @@
  */
 
 import java
+import PrintCfg
 
 external string selectedSourceFile();
 

java/ql/lib/semmle/code/java/ControlFlowGraph.qll

@@ -1788,4 +1788,7 @@ private module PrintGraphInput implements PrintGraph::InputSig<Location> {
   ControlFlowNode getASuccessor(ControlFlowNode n, SuccessorType t) { result = n.getASuccessor(t) }
 }
 
-import PrintGraph::PrintGraph<Location, PrintGraphInput>
+/** Provides utilities for visualising the CFG. */
+module PrintCfg {
+  import PrintGraph::PrintGraph<Location, PrintGraphInput>
+}