* eval.c (eval): not enforce to make assigned variables dynamic.
* parse.y (string): split rules to strings/xstring/regexp to allow
arbitrary statements inside string interpolation.
* parse.y (here_document): splitted into three phases.
* parse.y (literall_append, literal_concat): added.
append/concatinate string literals.
* sample/test.rb (valid_syntax): adjust line number for BEGIN.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@2590 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
