Enable QT_NO_CAST_FROM_ASCII & QT_NO_CAST_TO_ASCII

* Added a couple of utility macros to help with the conversion. lit() is
  paired with tr() for untranslated text.
* QFormatStr is more explicitly for non-textual formatting strings.
* Both are just #define'd to QStringLiteral()

qrenderdoc/Widgets/BufferFormatSpecifier.cpp

@@ -34,7 +34,7 @@ BufferFormatSpecifier::BufferFormatSpecifier(QWidget *parent)
 
   QObject::connect(ui->toggleHelp, &QPushButton::clicked, this, &BufferFormatSpecifier::toggleHelp);
 
-  setErrors("");
+  setErrors(QString());
 
   ui->formatText->setFont(QFontDatabase::systemFont(QFontDatabase::FixedFont));
 }
@@ -81,6 +81,6 @@ void BufferFormatSpecifier::showHelp(bool help)
 
 void BufferFormatSpecifier::on_apply_clicked()
 {
-  setErrors("");
+  setErrors(QString());
   emit processFormat(ui->formatText->toPlainText());
 }