[CVS ci] first MMD call

[Leopold Toetsch]

The two plain subroutine calls C<foo(f, b)> and C<foo(b, f)> with 
objects "f isa Foo" and "b isa Bar" are calling the subroutines Foo.foo 
and Bar.foo respectively. See the last test in t/pmc/mmd.t.

Not much more will work currently as function signatures are still missing.
The MultiSub object "foo" in the global namespace that triggers the MMD 
search is hand-crafted in main.

The function call signature is created in the S0 register, the call 
sequence looks basically like this:

  set P5, f      # get arg1
  set P6, b      # get arg2
  set I0, 1      # prototyped call
  set I1, 0      # 0 int args
  set I2, 0      # 0 string args
  set I3, 2      # 2 PMC args
  set I4, 0      # 0 float args
  set S0, "PP"   # signature
  find_name P0, "foo"
  invokecc
The whole register setup for I0..I4 is basically useless, as it doesn't 
contain the order of the call arguments that is needed to find the 
appropriate multi sub. E.g.:

  foo(int, float)
  foo(float, int)
would both have I1 = I4 = 1.
We have to adjust calling conventions eventually .
Related changes:
- parrotlib.imc did call function in the ::internal namespace w/o lookup
- adjusted call sequence so that find_name can investigate arguments
- if the C<find_name> opcode encounters a MultiSub object, MMD search is 
done

leo