* thread.c (update_coverage): Do not track coverage in loaded files
	  after Coverage.result. Avoids out-of-bounds access. [Bug #12237]

	* ext/coverage/coverage.c (coverage_clear_result_i): document.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54632 b2dd03c8-39d4-4d8f-98ff-823fe69b080e