* gc.c (rb_mark_set): new function to mark keys.
	* marshal.c (struct dump_arg, struct load_arg): added wrappers to mark
	  data entries.  backport from trunk r13527,r13528,r13961,r16533.
	  [ruby-dev:36082]
	* marshal.c (marshal_load): arg.data is no longer a VALUE but a
	  st_table, and freed in load_ensure.  pointed out by pegacorn.
	  [ruby-dev:37008]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8_7@21731 b2dd03c8-39d4-4d8f-98ff-823fe69b080e