forward references in typedefs

[mccaugh at s.cs.uiuc.edu]

 I couldn't help but side with the suggestion of "quadratic" even if it was
 misguided, since:

 * a 'quadrille' is a "square" dance, but consists of 5 or 6 rhythms
 * a 'quadrangle' and a 'quadrilateral' are both 4-sided
 * a 'quadrennium' is a period of 4 years

 Need I go on? THe point being that 'quadratic' means 'square', and it is
 an inference that the latter means "to the power 2".