Ruby

internal.h: fix potential memory leak

• internal.h (rb_imemo_tmpbuf_auto_free_pointer_new_from_an_RString):
  create tmpbuf to keep the pointer before xmalloc which can raise
  a NoMemoryError exception. extracted from
  https://github.com/bear-metal/ruby/tree/transient-imemo-tmpbuf

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67459 b2dd03c8-39d4-4d8f-98ff-823fe69b080e