Fix #77 add comment to headers in wrong order

src/sysinfo.cc

@@ -21,7 +21,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/resource.h>
-#include <sys/types.h>
+#include <sys/types.h> // this header must be included before 'sys/sysctl.h' to avoid compilation error on FreeBSD
 #include <sys/sysctl.h>
 #include <sys/time.h>
 #include <unistd.h>