Recognize dwarf::DW_ATE_UTF in DwarfUnit isUnsignedDIType

[dblaikie]

Summary

This patch fixes an assert violation triggered by the following clang test case:

// compile with -std=c++11 -g
const char16_t c = 0;
char16_t test() { return c; }

David, you wrote you could help me turn this into an LLVM test case?

[dblaikie]

Committed with a test case in r209037.

lib/CodeGen/AsmPrinter/DwarfUnit.cpp

static bool isUnsignedDIType(DwarfDebug *DD, DIType Ty) {
 
   DIBasicType BTy(Ty);
   assert(BTy.isBasicType());
   unsigned Encoding = BTy.getEncoding();
   assert((Encoding == dwarf::DW_ATE_unsigned ||
           Encoding == dwarf::DW_ATE_unsigned_char ||
           Encoding == dwarf::DW_ATE_signed ||
           Encoding == dwarf::DW_ATE_signed_char ||
+          Encoding == dwarf::DW_ATE_UTF ||
           Encoding == dwarf::DW_ATE_boolean) && "Unsupported encoding");
   return (Encoding == dwarf::DW_ATE_unsigned ||
           Encoding == dwarf::DW_ATE_unsigned_char ||
+          Encoding == dwarf::DW_ATE_UTF ||
           Encoding == dwarf::DW_ATE_boolean);
 }
 
 /// If this type is derived from a base type then return base type size.
 static uint64_t getBaseTypeSize(DwarfDebug *DD, DIDerivedType Ty) {
   unsigned Tag = Ty.getTag();
 
   if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&