string.c: r45621

* string.c (str_buf_cat): revert r45621.  this function does not
  scan appended data.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45623 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

string.c

@@ -2024,7 +2024,7 @@ str_buf_cat(VALUE str, const char *ptr, long len)
     if (ptr >= RSTRING_PTR(str) && ptr <= RSTRING_END(str)) {
         off = ptr - RSTRING_PTR(str);
     }
-    str_modify_keep_cr(str);
+    rb_str_modify(str);
     if (len == 0) return 0;
     if (STR_EMBED_P(str)) {
 	capa = RSTRING_EMBED_LEN_MAX;