Use the OpenBSD SQLCipher shared library when systemlib is enabled.

Index: direct-sqlcipher.cabal
--- direct-sqlcipher.cabal.orig
+++ direct-sqlcipher.cabal
@@ -80,3 +80,4 @@
   if flag(systemlib)
-    extra-libraries: sqlite3
+    extra-libraries: sqlcipher
+    include-dirs: /usr/local/include/sqlcipher
     cpp-options:     -Ddirect_sqlite_systemlib
