core/network: Add network abstraction

This commit adds a network abstraction designed to implement bsd:s but
at the same time work as a generic abstraction to implement any
networking code we have to use from core.

This is implemented on top of BSD sockets on Unix systems and winsock on
Windows. The code is designed around winsocks having compatibility
definitions to support both BSD and Windows sockets.

src/core/CMakeLists.txt

@@ -586,6 +586,9 @@ add_library(core STATIC
     memory/dmnt_cheat_vm.h
     memory.cpp
     memory.h
+    network/network.cpp
+    network/network.h
+    network/sockets.h
     perf_stats.cpp
     perf_stats.h
     reporter.cpp