Fix lldb build on Mac.

[wttsugrii]

Summary

https://github.com/llvm-mirror/lldb/commit/e80f43fd78fa0fbc04d2d59b5713acb5d06c8308
greatly improved an API, but missed one more occurence of legacy usage.

This leads to:

if (extractor.GetHexBytes(&payload_bytes[0], payload_bytes.size(), '\xdd') != payload_bytes.size())
                              ~~~~~~~~~~~~~~~~~~~~~                                          ^~~~~~
/lldb/include/lldb/Utility/StringExtractor.h:151:5: note: 'GetHexBytes' declared here

lldb/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp

DoExecute (Args& command, CommandReturnObject &result)
                                 const size_t ascii_hex_bytes_cstr_len = extractor.GetStringRef().size();
                                 if (ascii_hex_bytes_cstr_len & 1)
                                 {
                                     result.AppendErrorWithFormat ("payload data must contain an even number of ASCII hex characters: '%s'", ascii_hex_bytes_cstr);
                                     result.SetStatus (eReturnStatusFailed);
                                     return false;
                                 }
                                 payload_bytes.resize(ascii_hex_bytes_cstr_len/2);
-                                if (extractor.GetHexBytes(&payload_bytes[0], payload_bytes.size(), '\xdd') != payload_bytes.size())
+                                if (extractor.GetHexBytes(payload_bytes, '\xdd') != payload_bytes.size())
                                 {
                                     result.AppendErrorWithFormat ("payload data must only contain ASCII hex characters (no spaces or hex prefixes): '%s'", ascii_hex_bytes_cstr);
                                     result.SetStatus (eReturnStatusFailed);
                                     return false;
                                 }
                             }
                             Error error;
                             DataExtractor reply;