0.7.8.6:

0.7.8.6:
	made the debugger no longer rebind *PRINT-PRETTY*, since it
		made it unnecessarily difficult to debug problems
		involving PRINT-OBJECT bugs, and was just too DWIMish
	As long as I'm killing DWIMish things in INVOKE-DEBUGGER,
		comment out the sigsetmask(0).
	As long as as I'm cleaning up pretty-printer-related stuff,
		get rid of *PRETTY-PRINTER* too. (Since in ANSI the
		pretty printer is not an optional add-on, we shouldn't
		need the Spice-Lisp-ish hook to support the addition
		of a pretty printer.)