Check if OpenSSL is loaded.

Since we changed from `Digest::HMAC` to `OpenSSL::HMAC`, we should check
for if `OpenSSL` is loaded, and then we can safely assume that `HMAC` is
available. Before `Digest` was always defined, so we had to check if
it had loaded its submodules.

Author: Tobias Haagen Michaelsen

lib/openid/cryptutil.rb

@@ -37,7 +37,7 @@ def CryptUtil.sha1(text)
     end
 
     def CryptUtil.hmac_sha1(key, text)
-      if OpenSSL.const_defined? :HMAC, false
+      if defined? OpenSSL
         OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, key, text)
       else
         return HMAC::SHA1.digest(key, text)
@@ -49,7 +49,7 @@ def CryptUtil.sha256(text)
     end
 
     def CryptUtil.hmac_sha256(key, text)
-      if OpenSSL.const_defined? :HMAC, false
+      if defined? OpenSSL
         OpenSSL::HMAC.digest(OpenSSL::Digest::SHA256.new, key, text)
       else
         return HMAC::SHA256.digest(key, text)