C++: Fix some QLDoc holes.

cpp/ql/lib/semmle/code/cpp/dataflow/ExternalFlow.qll

@@ -375,10 +375,12 @@ private string paramsStringPart(Function c, int i) {
  * Parameter types are represented by their type erasure.
  */
 cached
-string paramsString(Function c) { result = concat(int i | | paramsStringPart(c, i) order by i) }
+private string paramsString(Function c) {
+  result = concat(int i | | paramsStringPart(c, i) order by i)
+}
 
 bindingset[func]
-predicate matchesSignature(Function func, string signature) {
+private predicate matchesSignature(Function func, string signature) {
   signature = "" or
   paramsString(func) = signature
 }

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

@@ -1046,6 +1046,10 @@ class DataFlowCallable extends TDataFlowCallable {
     this = TSummarizedCallable(result)
   }
 
+  /**
+   * Gets the underlying `Declaration` of this `DataFlowCallable`. This
+   * predicate returns a result for both source and summarized callables.
+   */
   Cpp::Declaration getUnderlyingCallable() {
     result = this.asSummarizedCallable() or // SummarizedCallable = Function (in CPP)
     result = this.asSourceCallable()

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

@@ -743,6 +743,10 @@ class InitialGlobalValue extends Node, TInitialGlobalValue {
  * of a models-as-data modeled function.
  */
 class FlowSummaryNode extends Node, TFlowSummaryNode {
+  /**
+   * Gets the models-as-data `SummaryNode` associated with this dataflow
+   * `FlowSummaryNode`.
+   */
   FlowSummaryImpl::Private::SummaryNode getSummaryNode() { this = TFlowSummaryNode(result) }
 
   /**