64-bit clean + WARNS=6:

64-bit clean + WARNS=6:
	- Convert the (char *) cast+cast backs magic to
	  memcpy(3).  Without this, the resulting code
	  is potentially risky with higher optimization
	  levels.
	- Avoid same name when calling local variables,
	  as well as global symbols.  This reduces
	  confusion for both human and compiler.
	- Add necessary casts, consts
	- Use new style function defination.
	- Minor style.Makefile(5) tweak
	- Bump WARNS?= from 0 to 6

** for the aout code: changes are intentionally limited
   to ease maintaince.