try_const

# File lib/mkmf.rb, line 1260
  def try_const(const, headers = nil, opt = "", &b)
    const, type = *const
    if try_compile(#{cpp_include(headers)}/*top*/typedef #{type || 'int'} conftest_type;conftest_type conftestval = #{type ? '' : '(int)'}#{const};, opt, &b)
      $defs.push(format("-DHAVE_CONST_%s", const.tr_cpp))
      true
    else
      false
    end
  end