[analyzer] Rename addTrackNullOrUndefValueVisitor to trackNullOrUndefValue.

This helper function (in the clang::ento::bugreporter namespace) may add more
than one visitor, but conceptually it's tracking a single use of a null or
undefined value and should do so as best it can.

Also, the BugReport parameter has been made a reference to underscore that
it is non-optional.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@162720 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp b/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp
index caf5b29..afab339 100644
--- a/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp
@@ -49,7 +49,7 @@
                                   "for @synchronized"));
       BugReport *report =
         new BugReport(*BT_undef, BT_undef->getDescription(), N);
-      bugreporter::addTrackNullOrUndefValueVisitor(N, Ex, report);
+      bugreporter::trackNullOrUndefValue(N, Ex, *report);
       C.EmitReport(report);
     }
     return;
@@ -72,7 +72,7 @@
                                    "(no synchronization will occur)"));
         BugReport *report =
           new BugReport(*BT_null, BT_null->getDescription(), N);
-        bugreporter::addTrackNullOrUndefValueVisitor(N, Ex, report);
+        bugreporter::trackNullOrUndefValue(N, Ex, *report);
 
         C.EmitReport(report);
         return;