GHC 7.5 moved a few functions and removed instance constraints.
Add Num to constraints with Bits
Bits no longer implies Num as of GHC 7.5
Use unsafePerformIO from System.IO.Unsafe
Foreign.unsafePerformIO is deprecated as of GHC 7.5
Use unsafeForeignPtrToPtr from Foreign.ForeignPtr.Unsafe
Export from Foreign.ForeignPtr deprecated as of GHC 7.5
You missed unsafePerformIO import (via Foreign) in OpenSSL/BN.hs
Thank you very much for your patch. I'll merge it within a few days, along with the same fix for OpenSSL.BN as pointed out by Mikhail. Sorry for the delay.
Applied and released HsOpenSSL-0.10.1.3. Thanks for your patience.