Get rid of magic open-coded register numbers. We now keep track of
a total of three different kinds of register numbers: the register
enumeration (regs.h), the x86 register value, and the register flags.
That has all the information we need.
Additionally, do massive revamping of the EA generation code and the
REX generation logic.
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.
