numeric literal without digits. based on a patch from ujihisa .
in [ruby-dev:39811]. [ruby-dev:39798]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@25962 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* parse.y (xstring, regexp, dsym, literal_concat, evstr2dstr):
literal at the top of dstr is no longer needed if it is empty,
since concatstrings and toregexp always create new strings.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24212 b2dd03c8-39d4-4d8f-98ff-823fe69b080e