order.  formerly check was done by dictionary order.
  [ruby-talk:74138]

* string.c (rb_string_value): fill constant empty string along
  with setting ELTS_SHARED if str->ptr is NULL. [ruby-core:01179]

* string.c (rb_string_value_ptr): ditto.

* string.c (rb_check_string_type): ditto.

* string.c (str_gsub): move END(0) check before mbclen2().

* string.c (scan_once): reduce END(0) check.

* io.c (rb_io_initialize): accept fixnum mode.

* eval.c (error_print): replace strchr() by memchr(), einfo may
  contain "\0".

* pack.c (pack_unpack): range check for "@" move; initialize check
  for "m".

* error.c (syserr_initialize): avoid buffer overflow.

* file.c (rb_file_s_readlink): expand buffer until readlink
  succeed.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@3982 b2dd03c8-39d4-4d8f-98ff-823fe69b080e