Fix subclassp for T class

[hemml]

The class T has no superclassess, so internal CLOS function SUBCLASSP, which is involved in appropriate method computation, returns NIL if both arguments are T:

CL-USER> (defclass c1 () ())

#<STANDARD-CLASS C1>
CL-USER> (jscl::subclassp (find-class 'c1) (find-class 'c1))
T
CL-USER> (jscl::subclassp (find-class T) (find-class T))
NIL

[hemml]

Can anybody merge this PR? It blocks me from updating OMGlib to the latest JSCL. Some CLOS methods cannot be called if they have mixed typed and untyped arguments: T sometimes not treated as a subclass of T.

[kchanqvq]

Let me take a look. I think it's probably better to fix the class precedence list of T.

[hemml]

Anyway, this fix will speedup check for the most common cases. It will be great to fix also the class precedence, of course.

[kchanqvq]

It's good to optimize performance, and in that case is eq better than equal? (Also let's state the commit message as performance improvement)

[hemml]

I'm not a professional Lisp programmer (or even a programmer in general), so I'm just following my tutorial recommendation to use equal for safety) Yes, eq will be faster there.

[davazp]

Sorry I missed this PR! I saw it but I thought I merged it.

Let me known if you want to change equal to eq or leave and I’ll merge it.

[kchanqvq]

The bug is already fixed in #625 btw, so this is just optimization.