Returns the thickness that should be used when drawing underlines with the receiver, as determined by the font’s AFM file.
Original signature is '- (CGFloat)underlineThickness'
Available in Mac OS X v10.0 and later.


- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)