Handle branches in VFPU delay slots better.

Based on tests on a PSP, all branches are attempted.  The behavior is
technically undefined.

It seems to take the delay slot's target if they differ and both pass.
This is the behavior the interpreter has, but it's more work in jit.

Since only a couple games seem to do this, and clearly expect this
behavior, this fixes all known cases of #1926.
Add a safety check for delay slot VFPU branches.

If the targets are different our behavior is probably wrong.