[parrot/parrot] dd3f6b: Fix g++ build errors

[noreply at github.com]

  Branch: refs/heads/whiteknight/pmc_is_ptr
  Home:   https://github.com/parrot/parrot

  Commit: dd3f6b86f1ba5a21684444b520859b5dc77c74fd
      https://github.com/parrot/parrot/commit/dd3f6b86f1ba5a21684444b520859b5dc77c74fd
  Author: Brian Gernhardt <brian.gernhardt at mail.rit.edu>
  Date:   2011-09-04 (Sun, 04 Sep 2011)

  Changed paths:
    M src/gc/fixed_allocator.c

  Log Message:
  -----------
  Fix g++ build errors

g++ is far pickier about casts, and it's good to make these things
explicit.