Implemented macros to abstract BIF parameter access/checks.

Avoid the assumption that if param n is omitted, param n+1 can't be
present.  This allows for things like InStr(H,N,,P) to become possible
in a future update.
Added SYM_MISSING for omitting parameters mid-param-list.
Refactored Func::Call().

- Handle caller-supplied array of params up front to simplify the rest.
- Support variadic object assignments like x[y*] := z.
- Use the stack rather than malloc, for performance.  This considerably
  improves speed of variadic calls to built-in functions/objects.  May
  be more due to cache utilization than malloc overhead.
- Handle all formal params in one loop, since "missing" params can now
  be mixed with actual "supplied" params.
Merge branch 'edge'
v1.1.12.00