fix breakage from recent syscall commits due to missing errno macros

src/linux/epoll.c

@@ -1,5 +1,6 @@
 #include <sys/epoll.h>
 #include <signal.h>
+#include <errno.h>
 #include "syscall.h"
 
 int epoll_create(int size)

src/linux/eventfd.c

@@ -1,5 +1,6 @@
 #include <sys/eventfd.h>
 #include <unistd.h>
+#include <errno.h>
 #include "syscall.h"
 
 int eventfd(unsigned int count, int flags)

src/linux/inotify.c

@@ -1,4 +1,5 @@
 #include <sys/inotify.h>
+#include <errno.h>
 #include "syscall.h"
 
 int inotify_init()