cocoa.messages: bind classname.methodname selectors also.

cocoa.messages: bind classname.methodname selectors also.

We currently have a problem which is all selectors are assumed to have
the same method effect.  The problem is we can have method collisions,
for example:

NSObject.load is { void { id SEL } }
NSBundle.load is { char { id SEL } }

So, this inferred wrong:

IN: scratchpad [ NSBundle -> mainBundle -> load ] infer .
( -- )

But now we can do this instead:

IN: scratchpad [ NSBundle -> NSBundle.mainBundle -> NSBundle.load ] infer .
( -- x )

It doesn't really fix the original problem, but its a way to workaround
it and added ``method-collisions`` to report on the conflicts.