Fix format specifier mismatch in XMLUtil::ToStr

In the XMLUtil::ToStr( uint64_t v, char* buffer, int bufferSize ) function, the format specifier %llu was used with a signed long long argument. This caused a type mismatch warning. The argument has been changed to unsigned long long to match the format specifier, resolving the warning.

tinyxml2.cpp

@@ -605,7 +605,7 @@ void XMLUtil::ToStr( int64_t v, char* buffer, int bufferSize )
 void XMLUtil::ToStr( uint64_t v, char* buffer, int bufferSize )
 {
  // horrible syntax trick to make the compiler happy about %llu
- TIXML_SNPRINTF(buffer, bufferSize, "%llu", (long long)v);
+ TIXML_SNPRINTF(buffer, bufferSize, "%llu", static_cast<unsigned long long>(v));
 }
 
 bool XMLUtil::ToInt(const char* str, int* value)