Refactor bad callee check into a Checker.
Now bad callee is checked as a PreVisit to the CallExpr.

llvm-svn: 80771
diff --git a/clang/lib/Analysis/BugReporterVisitors.cpp b/clang/lib/Analysis/BugReporterVisitors.cpp
index 5c31066..fce31e7 100644
--- a/clang/lib/Analysis/BugReporterVisitors.cpp
+++ b/clang/lib/Analysis/BugReporterVisitors.cpp
@@ -63,7 +63,8 @@
 
 const Stmt*
 clang::bugreporter::GetCalleeExpr(const ExplodedNode *N) {
-  const Stmt *S = N->getLocationAs<PostStmt>()->getStmt();
+  // Callee is checked as a PreVisit to the CallExpr.
+  const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
   if (const CallExpr *CE = dyn_cast<CallExpr>(S))
     return CE->getCallee();
   return NULL;