* configure.in: use quadrigraphs. workaround for autoconf 2.64.
  a patch provided by Hessob Park. [ruby-core:53157] [Backport #8020]



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40489 b2dd03c8-39d4-4d8f-98ff-823fe69b080e