PostgreSQL insert fails if the value is NaN in float type

Inserting NaN value to a PostgrSQL database requires apostrophes around it. QPSQL doesn't add those and the insertion fails with

QSqlError("42703", "QPSQL: Unable to create query", "ERROR: column "nan" does not exist
LINE 1: EXECUTE qpsqlpstmt_1 (nan)

This problem has been fixed for double type in https://bugreports.qt.io/browse/QTBUG-3088. Equal check in QPSQLDriver::formatValue() for float type would do the trick, which leads to another minor "problem" that QSqlField.type is QVariant::Type, which doesn't have the float type.

Tested with following code snippet:

QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
db.setDatabaseName("postgres");
QSqlQuery query;
query.exec("create table foo (id int primary key, "
                   "bar float)");
query.prepare("insert into foo values(1, :fValue)");
query.bindValue(":fValue", static_cast<float>(qQNaN()));
qDebug() << query.lastError() << query.exec();