title: Can't install openssl-devel for Python 2.7.11
body: <p>when i install the cryptography,there have some errors,for the platform is :</p>
  
  <pre><code>[root@RHanible ~]# python -V
  Python 2.7.11
  [root@RHanible ~]# rpm -qa openssl
  openssl-1.0.0-20.el6.x86_64
  [root@RHanible ~]# rpm -qa openssl-devel
  openssl-devel-1.0.0-20.el6.x86_64
  [root@RHanible ~]# rpm -qa python-devel
  python-devel-2.6.6-29.el6.x86_64
  [root@RHanible ~]# cat /etc/redhat-release 
  Red Hat Enterprise Linux Server release 6.2 (Santiago)
  </code></pre>
  
  <p>the errors is following:</p>
  
  <pre><code>already up-to-date
  building '_openssl' extension
  gcc -pthread -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/usr/local/python/include/python2.7 -c build/temp.linux-x86_64-2.7/_openssl.c -o build/temp.linux-x86_64-2.7/build/temp.linux-x86_64-2.7/_openssl.o
  build/temp.linux-x86_64-2.7/_openssl.c:2078: warning: function declaration isn?. a prototype
  build/temp.linux-x86_64-2.7/_openssl.c:2079: warning: function declaration isn?. a prototype
  build/temp.linux-x86_64-2.7/_openssl.c:2080: warning: function declaration isn?. a prototype
  build/temp.linux-x86_64-2.7/_openssl.c:2105: warning: function declaration isn?. a prototype
  build/temp.linux-x86_64-2.7/_openssl.c:2163: warning: function declaration isn?. a prototype
  build/temp.linux-x86_64-2.7/_openssl.c: In function ?.cffi_const_CMS_DEBUG_DECRYPT?.
  build/temp.linux-x86_64-2.7/_openssl.c:8193: error: ?.MS_DEBUG_DECRYPT?.undeclared (first use in this function)
  build/temp.linux-x86_64-2.7/_openssl.c:8193: error: (Each undeclared identifier is reported only once
  build/temp.linux-x86_64-2.7/_openssl.c:8193: error: for each function it appears in.)
  error: command 'gcc' failed with exit status 1
  </code></pre>