Merge pull request #2634 from MathiasVP/overrideable-taint-sources

C++: Overrideable taint sources in DefaultTaintTracking

Author: jbj

cpp/ql/src/semmle/code/cpp/ir/dataflow/DefaultTaintTracking.qll

@@ -28,6 +28,8 @@ private predicate userInputInstruction(Instruction instr) {
   or
   userInputReturned(instr.getConvertedResultExpression())
   or
+  isUserInput(instr.getConvertedResultExpression(), _)
+  or
   instr.getConvertedResultExpression() instanceof EnvironmentRead
   or
   instr