string.c: wchar terminator

* string.c (rb_str_lstrip_bang, rb_str_rstrip_bang): terminate
  wchar strings with wchar 0.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48275 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-11-05

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48276 b2dd03c8-39d4-4d8f-98ff-823fe69b080e