Impose a reasonableness standard on the GUI Altpos (font-based) unit, mainly to deal with Windows ME and possibly others, which report font metrics that are too skinny.
Background: this was inspired by the recognition that the standard desktop font under Windows ME, which appears to be identical to the one used in Windows XP, nonetheless reports its size as being exactly half as wide. This was causing dialogs based on the font size to appear half as wide as normal when running under ME. The fix should eliminate that anomaly.
