64-bit support required some major changes to regs.dat; clean some of
it up (re-introduce patterns, where appropriate) and allow a single
register to belong to multiple disassembly classes; also keep track
of the x86 register number again.
a) Automatically generate dependencies for all Makefiles;
b) Move register definitions to a separate .dat file;
c) Add support for "unimplemented but there in theory" registers.
