[CM] Snd 20.1

[bil at ccrma.Stanford.EDU]

Snd 20.1:

s7: s7_c_type_set_is_equal|is_equivalent|gc_free|gc_mark
     debug.scm and (*s7* 'debug)
     removed coverlets (openlets is now a dilambda)

checked: sbcl 2.0.1

Thanks!: Woody Douglass, Kjetil Matheussen, Rick Taube, Mike Scholz