Add 2 new archsw interfaces:

1. arch_loadaddr - used by platform code to adjust the address at which the object gets loaded. Implement PC98 using this new interface instead of using conditional compilation. For ELF objects the ELF header is passed as the data pointer. For raw files it's the filename. Note that ELF objects are first considered as raw files.
2. arch_loadseg - used by platform code to keep track of actual segments, so that (instruction) caches can be flushed or translations can be created. Both the ELF header as well as the program header are passed to allow platform code to treat the kernel proper differently from any additional modules and to have all the relevant details of the loaded segment (e.g. protection).