revert re.c in r53736

* re.c (rb_reg_initialize): must copy the source string content,
  it is not a static literal.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53738 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -3,8 +3,6 @@ Thu Feb  4 15:35:29 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 	* string.c (rb_fstring_enc_new, rb_fstring_enc_cstr): functions to
 	  make fstring with encoding.
 
-	* re.c (rb_reg_initialize): make fstring without copying.
-
 Thu Feb  4 14:42:29 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* common.mk: Added Unicode data file SpecialCasing.txt to be additionally

re.c

@@ -2580,7 +2580,7 @@ rb_reg_initialize(VALUE obj, const char *s, long len, rb_encoding *enc,
 			  options & ARG_REG_OPTION_MASK, err,
 			  sourcefile, sourceline);
     if (!re->ptr) return -1;
-    RB_OBJ_WRITE(obj, &re->src, rb_fstring_enc_new(s, len, enc));
+    RB_OBJ_WRITE(obj, &re->src, rb_fstring(rb_enc_str_new(s, len, enc)));
     RB_GC_GUARD(unescaped);
     return 0;
 }