[perl #47113] UNIVERSAL::can is wrong for unloaded classes

I've pushed a fix for this to the doy/universal branch. It's pretty
straightforward, but some of the tests in t/op/universal.t were testing
for this behavior explicitly (checking that can() was false before a
package existed and true afterwards), so I'm not sure if this is
reasonable to just change directly. I am in favor of making this change
though, so any input is welcome.

• [perl #47113] UNIVERSAL::can is wrong for unloaded classes by Jesse Luehrs via RT
• [perl #47113] UNIVERSAL::can is wrong for unloaded classes by Father Chrysostomos via RT
• Re: [perl #47113] UNIVERSAL::can is wrong for unloaded classes by Jesse Luehrs
• [perl #47113] UNIVERSAL::can is wrong for unloaded classes by Father Chrysostomos via RT
• [perl #47113] UNIVERSAL::can is wrong for unloaded classes by Jesse Luehrs via RT
• Re: [perl #47113] UNIVERSAL::can is wrong for unloaded classes by Ricardo Signes