* Tweak make-config.sh to automatically select GENCGC, and to
update the fallback message for those poor bsd-using folks.
* Copied the gencgc memory map from the SunOS version to use for
Linux (the cheneygc maps were identical, we may as well keep the
* Also tweaked the linker flags to match. Not because it was
required to build, but because I don't know why they were changed
for SunOS, and in the absence of such knowledge I'd rather keep
things more or less parallel.