fix constant-list-related initargs in CTOR optimization

lp#1099708, reported by Derek Baldwin; also test for _3b's #sbcl irc insight
that this would break non-EQLity of distinct but EQUAL list constants

Also deal with pathnames, bit-vectors and strings, which are precisely the
types EQUAL descends into.

(The general problem of function names being looked up using EQUAL remains
a problem, though with fewer observable consequences: for example, methods
with EQUAL eql-specializers will have their function names collide with
each other, though since in CLOS the functions are looked up through the
method objects this is less serious than with CTORs.