* gc.c (vm_xrealloc): add a few comment why we avoid realloc(ptr,0).

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38696 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-01-05

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38697 b2dd03c8-39d4-4d8f-98ff-823fe69b080e