If a .c file included "types.h" before "mach.h", then it missed the
declaration of mach_option(). Fix by adding "xmach.h".
Fix mach/powerpc/ncg/mach.h and mach/vc4/ncg/mach.h to use the correct
type in their printf() format strings.
Files that #include "equiv.h" must do so after including "data.h", now
that a function prototype in equiv.h uses type rl_p from data.h.
Adjust style, changing some `for(...)` to `for (...)`. The style in
mach/proto/ncg is less than consistent; the big annoyance now is that
some files want tabs at 4 spaces, others want tabs at 8 spaces.
Put the declarations in "data.h", because that header declares the
types cost_t and token_p. Also #include <cgg_cg.h> from "data.h" to
get types c3_p and set_p, and guard <cgg_cg.h> against multiple
inclusion.
