How to reproduce:
```
$ cabal configure -f-support_deepseq
Resolving dependencies...
Configuring cryptonite-0.23...
$ cabal build
Building cryptonite-0.23...
Preprocessing library cryptonite-0.23...
[114 of 120] Compiling Crypto.PubKey.RSA.Types ( Crypto/PubKey/RSA/Types.hs, dist/build/Crypto/PubKey/RSA/Types
Crypto/PubKey/RSA/Types.hs:48:30: error:
• No instance for (NFData Integer) arising from a use of ‘rnf’
• In the first argument of ‘seq’, namely ‘rnf n’
In the expression: rnf n `seq` rnf e `seq` sz `seq` ()
In an equation for ‘rnf’:
rnf (PublicKey sz n e) = rnf n `seq` rnf e `seq` sz `seq` ()
```
The fix is to inctoruce 'NFData Integer' instance to `Crypto/Internal/DeepSeq`.
Closes: https://github.com/haskell-crypto/cryptonite/issues/171
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
