Add maniplator for QLineEdit maxLength property in QFileDialog

QFileDialog has a QLineEdit.

The default maxLength for QLineEdit is 32767 characters. This makes it impossible to select large numbers of files with large filenames.

QFileDialog hides its QLineEdit behind the PIMPL idiom, preventing developers from accessing it via subclass or otherwise, without modifying Qt source code directly.

Please add a manipulator for this property to the QFileDialog interface.