Include <sys/select.h> for fd_set

When fd_set is used <sys/select.h> should be included.
On glibc it is done implicitly via other headers,
on musl it must be explicitly provided.

Signed-off-by: Andrew Savchenko <bircoph@gentoo.org>

api/epplet.c

@@ -3,6 +3,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/resource.h>
+#include <sys/select.h>
 #include <sys/utsname.h>
 #include <signal.h>
 #include <sys/time.h>

epplets/E-Pinger.c

@@ -32,6 +32,7 @@
 
 #include <errno.h>
 #include <signal.h>
+#include <sys/select.h>
 #include <sys/wait.h>
 
 #include "config.h"

epplets/E-SD.c

@@ -19,6 +19,7 @@
  */
 #include <esd.h>
 #include <fcntl.h>
+#include <sys/select.h>
 
 #include "config.h"
 #include "epplet.h"

epplets/E-ScreenShoot_ftp.c

@@ -5,6 +5,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
+#include <sys/select.h>
 
 #include "E-ScreenShoot_ftp.h"