* ext/psych/lib/psych/syntax_error.rb: Psych::SyntaxError now inherits
from StandardError rather than SyntaxError. Thanks Eric Hodel!
* test/psych/test_exception.rb: tests for change.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37292 b2dd03c8-39d4-4d8f-98ff-823fe69b080e