help badly needed - PMC compiler

[Leopold Toetsch]

I'm still restructuring the MMD infix functions and classes. Divide and 
floor_divide are done. But there is a problem:

* the Float PMC isa(scalar): it inherits almost all mathemtical 
functions from the abstract "scalar" PMC

* But e.g Parrot_Float_subtract_Complex isn't inherited automatically, 
only functions that have an equivalent in vtable.tbl are inherited but 
not MMD variants. I've currently hard-coded the _subtract_Complex 
functions to make tests happy. But when looking at classes/float.c you 
can see that e.g. MMD_ADD doesn't have the proper add_Complex function.

The goal is therefore to properly inherit all MMD variants of a function 
from an abstract base class like "scalar".

Alternatively we could make "scalar" a true type:
  pmclass Scalar noinit does scalar { ... }
and just forbid instantiation. With this declaration it should have a 
vtable and proper MMD entries, which are inherited dynamically via the 
MRO. But that increases the MMD_table so I'd rather keep it abstract.

Thanks,
leo