Remove -Wspellcheck and replace it with a diagnostic option.

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

llvm-svn: 177218
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index fa59212..f6ba4e5 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -561,6 +561,7 @@
   Opts.VerifyDiagnostics = Args.hasArg(OPT_verify);
   Opts.ElideType = !Args.hasArg(OPT_fno_elide_type);
   Opts.ShowTemplateTree = Args.hasArg(OPT_fdiagnostics_show_template_tree);
+  Opts.WarnOnSpellCheck = Args.hasArg(OPT_fwarn_on_spellcheck);
   Opts.ErrorLimit = Args.getLastArgIntValue(OPT_ferror_limit, 0, Diags);
   Opts.MacroBacktraceLimit
     = Args.getLastArgIntValue(OPT_fmacro_backtrace_limit,