merge revision(s) 44432: [Backport #9299]

	* proc.c: Having optional keyword arguments makes maximum arity +1,
	  not unlimited [#8072]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@45231 b2dd03c8-39d4-4d8f-98ff-823fe69b080e