0.7.1.3:

0.7.1.3:
	added new condition type BUG...
	...defined BUG function to signal BUG
	...made AVER use BUG
	...systematically checked things matching '".*internal.*error'
		to see whether they should use BUG
	...picked off a few other things and made them use BUG too
	(apparently forgot to check it in, oops)
	partial fix for bug 147 (so that the new simpler test case
		compiles, but the original test case still fails with
		the original AVER failure)...
	...added "Don't close over unreferenced variables just because
		they're set" logic in %ADD-LAMBDA-VARS-TO-CLOSURES
	...(various other tidying while hunting for this problem)