string.c: suppress warnings

* string.c (rb_str_scrub): suppress maybe-uninitialized and empty body
  in an else-statement.  [ruby-dev:45975] [Feature #6752]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40416 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: fix for UTF-32

* string.c (rb_str_scrub): fix for UTF-32.  strlen() on strings
  contain NUL returns wrong result, use sizeof operator instead.
  [ruby-dev:45975] [Feature #6752]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40417 b2dd03c8-39d4-4d8f-98ff-823fe69b080e