CPP: Exclude unusual header files such as config.h.

Author: geoffw0

cpp/ql/src/Documentation/CommentedOutCode.qll

@@ -156,6 +156,7 @@ class CommentBlock extends Comment {
 
   predicate isCommentedOutCode() {
     not this.isDocumentation() and
+    not this.getFile().(HeaderFile).noTopLevelCode() and
     this.numCodeLines().(float) / this.numLines().(float) > 0.5
   }
 

cpp/ql/test/query-tests/Documentation/CommentedOutCode/CommentedOutCode.expected

@@ -1,6 +1,3 @@
-| config.h:9:1:9:18 | //#define SETTING3 | This comment appears to contain commented-out code |
-| config.h:12:1:12:22 | /* #define SETTING4 */ | This comment appears to contain commented-out code |
-| config.h:19:1:19:21 | /* #undef SETTING5 */ | This comment appears to contain commented-out code |
 | test2.cpp:37:1:37:39 | // int myFunction() { return myValue; } | This comment appears to contain commented-out code |
 | test2.cpp:39:1:39:45 | // int myFunction() const { return myValue; } | This comment appears to contain commented-out code |
 | test2.cpp:41:1:41:54 | // int myFunction() const noexcept { return myValue; } | This comment appears to contain commented-out code |