Fix CharByteWidth assertion in LiteralSupport.

Patch by Eelis van der Weegen.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190971 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/LiteralSupport.cpp b/lib/Lex/LiteralSupport.cpp
index 08d6c43..c637c38 100644
--- a/lib/Lex/LiteralSupport.cpp
+++ b/lib/Lex/LiteralSupport.cpp
@@ -336,7 +336,7 @@
     return;
   }
 
-  assert((CharByteWidth == 1 || CharByteWidth == 2 || CharByteWidth) &&
+  assert((CharByteWidth == 1 || CharByteWidth == 2 || CharByteWidth == 4) &&
          "only character widths of 1, 2, or 4 bytes supported");
 
   (void)UcnLen;