Merge NullDerefChecker.[h,cpp] and UndefDerefChecker.[h,cpp].  They are essentially two parts of the same check.

llvm-svn: 85911
diff --git a/clang/lib/Analysis/NSErrorChecker.cpp b/clang/lib/Analysis/NSErrorChecker.cpp
index 2f6df23e..307686f 100644
--- a/clang/lib/Analysis/NSErrorChecker.cpp
+++ b/clang/lib/Analysis/NSErrorChecker.cpp
@@ -18,7 +18,7 @@
 #include "clang/Analysis/LocalCheckers.h"
 #include "clang/Analysis/PathSensitive/BugReporter.h"
 #include "clang/Analysis/PathSensitive/GRExprEngine.h"
-#include "clang/Analysis/PathSensitive/Checkers/NullDerefChecker.h"
+#include "clang/Analysis/PathSensitive/Checkers/DereferenceChecker.h"
 #include "BasicObjCFoundationChecks.h"
 #include "llvm/Support/Compiler.h"
 #include "clang/AST/DeclObjC.h"