Fix some BSD portability issues

Thanks to mdg on the forum and the Debian buildd.

src/network/C4NetIO.h

@@ -39,6 +39,8 @@
 #define SOCKET int
 #define INVALID_SOCKET (-1)
 #include <arpa/inet.h>
+// for htons
+#include <netinet/in.h>
 #endif
 
 #ifdef HAVE_SYS_TYPES_H

src/platform/PlatformAbstraction.h

@@ -217,7 +217,7 @@ inline int stricmp(const char *s1, const char *s2)
 #elif defined(__APPLE__)
 #define C4_OS "mac-x86"
 #else
-#define C4_OS "unknown";
+#define C4_OS ""
 #endif
 
 // delete item to the recycle bin