Turn cl::values() (for enum) from a vararg function to using C++ variadic template

The core of the change is supposed to be NFC, however it also fixes
what I believe was an undefined behavior when calling:

 va_start(ValueArgs, Desc);

with Desc being a StringRef.

Differential Revision: https://reviews.llvm.org/D25342

llvm-svn: 283671
diff --git a/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp b/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp
index 7ee4ba1..fc37dea 100644
--- a/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp
+++ b/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp
@@ -46,8 +46,7 @@
                clEnumValN(FunctionNameKind::ShortName, "short",
                           "print short function name"),
                clEnumValN(FunctionNameKind::LinkageName, "linkage",
-                          "print function linkage name"),
-               clEnumValEnd));
+                          "print function linkage name")));
 
 static cl::opt<bool>
     ClUseRelativeAddress("relative-address", cl::init(false),