LOG_TO_STRING and std namespace

[blacktea]

Hi,
I'd like to use LOG_TO_STRING(ERROR,string) macros.
However, it requires to write
using namespace std; or using std::string;
before calling macros. That's not convinient.

That's because LOG_TO_STRING does not use std namespace in static_cast.

#define LOG_TO_STRING(severity, message) \ LOG_TO_STRING_##severity(static_cast<string*>(message)).stream()