* test/-ext-/ast/test_ast.rb: Add tests for Node
code locations. This file tests
1. There are no Node whose code location is default
value (#test_not_cared)
2. There are no Node whose children's code locations
exceed parent's code location (#test_ranges)
* ext/-test-/ast/ast.c, ext/-test-/ast/extconf.rb:
Define AST module to help tests.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61859 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
