merge revision(s) r45911,r45912,r45917,r45918,r45919: [Backport #9820]

	* signal.c (rb_f_kill): directly enqueue an ignored signal to self,
	  except for SIGSEGV and SIGBUS.  [ruby-dev:48203] [Bug #9820]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@47345 b2dd03c8-39d4-4d8f-98ff-823fe69b080e