[GC] --gc-debug was to restrictive
[GC] --gc-debug was to restrictive

* allocating  just 1 PObj (PMC,STRING,Buffer) per memory pool, 
  if --gc_debug is set, isn't really a good strategy for running
  more than a PIR one-line (tcl tests were totally starved with it)


git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@14336 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot