Remove -Wspellcheck and replace it with a diagnostic option.

Thanks to Richard S. for pointing out that the warning would show up
with -Weverything.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177218 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/Warnings.cpp b/lib/Frontend/Warnings.cpp
index 767096a..b7547b9 100644
--- a/lib/Frontend/Warnings.cpp
+++ b/lib/Frontend/Warnings.cpp
@@ -56,6 +56,7 @@
 
   Diags.setElideType(Opts.ElideType);
   Diags.setPrintTemplateTree(Opts.ShowTemplateTree);
+  Diags.setWarnOnSpellCheck(Opts.WarnOnSpellCheck);
   Diags.setShowColors(Opts.ShowColors);
  
   // Handle -ferror-limit