sceIoRename() ignores any path on dest

Also, change the interface so it can return an error code.  Currently not returning perfect error codes but it's better than before.

Thanks to @thedax for debugging Metal Gear Solid: Peace Walker.  It was simply failing to rename temporary files to dest files since it didn't qualify the destination path.  With this, it no longer complains about install every time.

May improve other games which use temp files to manage save or install data.

-[Unknown]