[asdf-devel] 3.1.0.75 pushed: more checking of system names

[Robert P. Goldman]

This is a repair of last night's commit.  I added a test for the new
system name checks, which had some fan-out -- I needed to fix
DEF-TEST-SYSTEM to permit systems named with strings instead of symbols.

Also, I check to make sure that all the system names, when being
registered, are case-flattened down, and issue a continuable error if not.

cheers,
r