LinGui: Add max width/height widgets to preset save dialog

LinGui: Add max width/height widgets to preset save dialog
These are only visible when autosize is disabled, meaning the user
has chosen to set specific video dimensions.  These values are used
when a preset or title is loaded to set the default storage dimensions.

This allows setting arbitrary PictureWidth/PictureHeight in the preset
which was not previously possible.  The values were previously limited
to what the currently loaded source would allow you to enter into
the picture settings width/height fields.

git-svn-id: svn://localhost/HandBrake/trunk@3417 b64f7644-9d1e-0410-96f1-a4d463321fa5