merge revision(s) 44853: [Backport #9490]

	* gc.c (ruby_gc_set_params): if RUBY_GC_OLDMALLOC_LIMIT is provided,
	  then set objspace->rgengc.oldmalloc_increase_limit.
	  Without this fix, the env variable RUBY_GC_OLDMALLOC_LIMIT
	  does not work.

	* gc.c (get_envparam_int): accept a value equals to lowerbounds.

	* gc.c (get_envparam_double): ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@44856 b2dd03c8-39d4-4d8f-98ff-823fe69b080e