Trapezoidal room generation/placement is slow

[glennmatthews]

Trapezoidal room generation and placement is noticeably slower than any other room type (causing the program to stall for several seconds before it completes). This is probably because a much larger number of candidate shapes are being considered (a "one-sided" trapezoid has 8 possible orientations, and we are generating several different sizes of such as well as "two-sided" trapezoids each with four possible orientations). We should look for ways to speed up this placement or reduce the number of options being considered.