string.c: check null char

* string.c (rb_string_value_cstr): check null char in char, not in
  byte.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41918 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: multi-byte terminator

* string.c (rb_string_value_cstr): fill minimum length of the encoding
  as the terminator.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41919 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: multi-byte terminator

* string.c (rb_enc_str_new, rb_str_set_len, rb_str_resize): fill
  minimum length of the encoding as the terminator.
* string.c (str_buf_cat, rb_str_buf_append, rb_str_splice_0): ditto.
* string.c (str_make_independent_expand, rb_str_modify_expand): make
  the capacity enough for multi-byte terminator.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41920 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
transcode.c: fill terminator

* transcode.c (str_encode_associate): fill terminator after conversion.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41921 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32/registry.rb: remove workaround

* ext/dl/win32/lib/win32/registry.rb (Win32::Registry::API#make_wstr):
  remove workaround to append WCHAR terminator.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41922 b2dd03c8-39d4-4d8f-98ff-823fe69b080e