hplip: unbreak musl (fd_set is declared in sys/select.h).

srcpkgs/hplip/patches/musl.patch

@@ -0,0 +1,10 @@
+--- protocol/discovery/mdns.c.orig	2015-11-17 09:58:44.171711728 +0100
++++ protocol/discovery/mdns.c	2015-11-17 09:59:11.347535726 +0100
+@@ -28,6 +28,7 @@
+ #include <string.h>
+ #include <syslog.h>
+ #include <sys/socket.h>
++#include <sys/select.h>
+ #include <netinet/in.h>
+ #include <netdb.h>
+ #include <arpa/inet.h>