Improve some of the conversion warnings to fire on conversion to bool.

Moves the bool bail-out down a little in SemaChecking - so now
-Wnull-conversion and -Wliteral-conversion can fire when the target type is
bool.

Also improve the wording/details in the -Wliteral-conversion warning to match
the -Wconstant-conversion.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156826 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/SemaCXX/expressions.cpp b/test/SemaCXX/expressions.cpp
index 355833e..2635fb8 100644
--- a/test/SemaCXX/expressions.cpp
+++ b/test/SemaCXX/expressions.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s 
+// RUN: %clang_cc1 -fsyntax-only -verify -Wno-constant-conversion %s
 
 void choice(int);
 int choice(bool);