cryptopp: add dylib to build

Seems like the there has been no inclusion of a previous patch like this [in the source tree](http://sourceforge.net/p/cryptopp/code/HEAD/tree/trunk/c5/GNUmakefile) (the one noted in the Google groups post from 3.5 years ago).  However, the lib's dev has posted a [link to it on the wiki](http://www.cryptopp.com/wiki/IOS_%28Xcode%29).