Fixed some stuff that caused errors in code compilation under Mac OS.

Changes in macdockiconhandler.h and macdockiconhandler.mm base on the
respective files from the litecoin project.
Bug in net.cpp was fixed based on a solution provided in the dogecoin
project.

With these changes auroracoin compiles on Mac (OS X 10.9) and runs (if the respective libs, i.e. boost, db48 and miniupnpc) are installed.