C#/Cfg: A bit more qldoc.

Author: aschackmull

csharp/ql/lib/semmle/code/csharp/controlflow/ControlFlowElement.qll

@@ -8,6 +8,7 @@ private import semmle.code.csharp.Caching
 
 private class TControlFlowElementOrCallable = @callable or @control_flow_element;
 
+/** A `ControlFlowElement` or a `Callable`. */
 class ControlFlowElementOrCallable extends ExprOrStmtParent, TControlFlowElementOrCallable { }
 
 /**

shared/controlflow/codeql/controlflow/ControlFlowGraph.qll

@@ -894,6 +894,7 @@ module Make0<LocationSig Location, AstSig<Location> Ast> {
       override string toString() { result = tag + " " + n }
     }
 
+    /** The `PreControlFlowNode` at the entry point of a callable. */
     final class EntryNodeImpl extends NodeImpl, TEntryNode {
       private Callable c;