Fix C++0x narrowing errors when char is unsigned.

In the case of EDInstInfo, this would actually cause a bug when -1 became 255
and was then compared >=0 in llvm-mc/Disassembler.cpp.

llvm-svn: 138825
diff --git a/llvm/unittests/VMCore/MetadataTest.cpp b/llvm/unittests/VMCore/MetadataTest.cpp
index 0b2c012..12ac2e7 100644
--- a/llvm/unittests/VMCore/MetadataTest.cpp
+++ b/llvm/unittests/VMCore/MetadataTest.cpp
@@ -63,7 +63,7 @@
 
 // Test printing of MDString with non-printable characters.
 TEST_F(MDStringTest, PrintingComplex) {
-  char str[5] = {0, '\n', '"', '\\', -1};
+  char str[5] = {0, '\n', '"', '\\', (char)-1};
   MDString *s = MDString::get(Context, StringRef(str+0, 5));
   std::string Str;
   raw_string_ostream oss(Str);