This is a new and faster UTF-8 encoder, based on the code from QUrl. This code
specializes for ASCII, which is the most common case anyway, especially since
QString's "ascii" mode is actually UTF-8 now.
In addition, make QString::toUtf8 use a stateless encoder. Stateless means that
the function doesn't handle state between calls in the form of
QTextCodec::ConverterState. This allows it to be faster than otherwise.
The new code is in the form of a template so that it can be used from
QJsonDocument and QUrl, which have small modifications to how the
encoding is handled.
Change-Id: I305ee0fd8523cc4ec74c2678cb9ea88b75bac7ac
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
d51130cc3a