Build 1710
SVN-
make sector keep old firstwall when adding inner loop, rewrite setfirstwall to use malloc'ed memory for temp storage instead of end of sector[], reintroduce correct searchwall determination in Polymer mouse picker (intersection of xy projection of aiming ray with wall); added commands to m32script: shiftvarvar[lr], ifhighlighted, ifin3dmode, updatehighlight, sethighlight; coded prototype terrain helper based on isolines and triangle strips.