This is a version of Tiny GC (see README file) preconfigured in
gc.c for AdLib's needs and using Doug Lea's malloc implementation
(in dlmalloc.c) instead of a potentially slow system malloc. In
particular, we don't use locks around dlmalloc() and dlfree(), as
we know that they will only be called from Tiny GC.

Note that dlmalloc.c is public domain and can be used separately
from Tiny GC's license. The gc.c file is distributed under Tiny
GC's license (the GPL v2, see COPYING).
