tinyformat: force USE_VARIADIC_TEMPLATES #8000

Now that we started using c++11, force use of variadic templates.

The autodetection may be wonky on some compilers, see discussion here and is unnecessary for us anyhow.

ut ACK

Looks like there is another tinyformat-related c++1 TODO here: https://github.com/bitcoin/bitcoin/blob/master/src/util.h#L83

utACK https://github.com/bitcoin/bitcoin/pull/8000/commits/9eaa0afa6ec5d3dd01e4d01121314ef51f2bc305

utACK 9eaa0af

utACK 9eaa0afa6ec5d3dd01e4d01121314ef51f2bc305

Added a second commit that makes LogPrint and error into variadic templates.

may as well use perfect forwarding here, since all args are universal references:

template<typename T1, typename... Args>
bool error(const char* fmt, T1&& v1, Args&&... args)
{
    LogPrintStr("ERROR: " + tfm::format(fmt, std::forward<T1>(v1), std::forward<Args>(args)...) + "\n");
...

@cfields I use the same convention as the functions in tinyformat.h itself now:

template<typename T1, typename... Args>
std::string format(const char* fmt, const T1& v1, const Args&... args)
{
    std::ostringstream oss;
    format(oss, fmt, v1, args...);
    return oss.str();
}

I'm not sure perfect forwarding would win anything unless it's done at all levels.

blah, I assumed if it used variadics it also forwarded nicely. Indeed, no point in changing.

ut ACK 08d7b563e91ed2ad226ec2505a5a850ab869d2f0

blah, I assumed if it used variadics it also forwarded nicely. Indeed, no point in changing.

Well I agree with changing it, but yea should probably do that at once throughout the entire thing, in a separate pull.