Disassembling 'custom' instructions

I've just put some patches onto the wiki page that fix the disassembly of custom instructions that have the readra/readrb/writerc bits clear.

I've also done some fixes for running on non 32bit hosts.

(like not using %u for 'unsigned long').

However I've not tried running the compiler (etc) on systems that are likely to be problematical (eg sparc64 or something where 'int' is 64bits).