* test/coverage/test_coverage.rb: ignored test when enabled to coverage.
	  It lead to crash with `make test-all`.

	* compile.c (ADD_TRACE): ignore trace instruction on non-positive
	  line.

	* parse.y (coverage): get rid of ArgumentError when the starting
	  line number is not positive.  [ruby-core:76141] [Bug #12517]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@55943 b2dd03c8-39d4-4d8f-98ff-823fe69b080e