Book 3 Listing 39: plane_origin, axis_A, and axis_B

[davidfrogley]

The code in Listing 39 (quad.h) in the override of the random method lists three member fields by, I believe, the wrong name (unless I missed something, which is certainly possible):

• plane_origin should be Q
• axis_A should be u
• axis_B should be v

[hollasch]

Spawned issue #1266.