Add a UTF8 to UTF16 conversion wrapper for use in the pdb dumper

This can also be used instead of the WindowsSupport.h ConvertUTF8ToUTF16
helpers, but that will require massaging some character types. The
Windows support routines want wchar_t output, but wchar_t is often 32
bits on non-Windows OSs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227122 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/ConvertUTF.h

@@ -251,6 +251,14 @@ bool hasUTF16ByteOrderMark(ArrayRef<char> SrcBytes);
  */
 bool convertUTF16ToUTF8String(ArrayRef<char> SrcBytes, std::string &Out);
 
+/**
+ * Converts a UTF-8 string into a UTF-16 string with native endianness.
+ *
+ * \returns true on success
+ */
+bool convertUTF8ToUTF16String(StringRef SrcUTF8,
+                              SmallVectorImpl<UTF16> &DstUTF16);
+
 } /* end namespace llvm */
 
 #endif