Diagnostics should start with a lower-case letter.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155936 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index ee883ae..7f2f2b5 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1536,7 +1536,7 @@
 def err_undeclared_nsstring : Error<
   "cannot box a string value because NSString has not been declared">;
 def err_objc_illegal_boxed_expression_type : Error<
-  "Illegal type %0 used in a boxed expression">;
+  "illegal type %0 used in a boxed expression">;
 def err_undeclared_nsarray : Error<
   "NSArray must be available to use Objective-C array literals">;
 def err_undeclared_nsdictionary : Error<