Provide -Wnull-conversion separately from -Wconversion.

Like GCC, provide a NULL conversion to non-pointer conversion as a separate
flag, on by default. GCC's flag is "conversion-null" which we provide for
cross compatibility, but in the interests of consistency (with
-Wint-conversion, -Wbool-conversion, etc) the canonical Clang flag is called
-Wnull-conversion.

Patch by Lubos Lunak.
Review feedback by myself, Chandler Carruth, and Chad Rosier.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152745 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Analysis/nullptr.cpp b/test/Analysis/nullptr.cpp
index c0fed87..3119b4f 100644
--- a/test/Analysis/nullptr.cpp
+++ b/test/Analysis/nullptr.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++11 -analyze -analyzer-checker=core -analyzer-store region -verify %s
+// RUN: %clang_cc1 -std=c++11 -Wno-conversion-null -analyze -analyzer-checker=core -analyzer-store region -verify %s
 
 // test to see if nullptr is detected as a null pointer
 void foo1(void) {