merge revision(s) 41325: [Backport #8554]

* gc.c: Fixup around GC by MALLOC.
  Add allocate size to malloc_increase before GC
  for updating limit in after_gc_sweep.
  Reset malloc_increase into garbage_collect()
  for preventing GC again soon.
  this backport patch is written by nari.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@41628 b2dd03c8-39d4-4d8f-98ff-823fe69b080e