Build fails with -DQT_NO_CAST_FROM_ASCII

[tim-gromeyer]

When -DQT_NO_CAST_FROM_ASCII is defined, you cant call QChar(' ')(char) and QString("String")(const char*).
To avoid the QChar error we could use QChar(u' ') but this requires Qt >= 5.10.
For QString we could use QStringLiteral.

I created a issue because i don't want to create a pull request that requires Qt 5.10 without having your OK.

[pbek]

Qt 5.5+ must be supported. So best use some #if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)) directives.
@Waqar144, any objections?

[Waqar144]

just QLatin1Char(...) should be enough for us I think.

[tim-gromeyer]

QLatin1Char doesn't work everywhere(for example here and here)