Always include <errno.h> instead of <sys/errno.h>

Including <sys/errno.h> instead of <errno.h> raises a compiler warning
when building against musl libc.  Always include <errno.h> instead of
<sys/errno.h> to prevent that compilation warning from being triggered
and to achieve consistency in this regard across the entire source tree.

bin/named/fuzz.c

@@ -17,7 +17,7 @@
 #ifdef ENABLE_AFL
 #include <named/globals.h>
 #include <named/server.h>
-#include <sys/errno.h>
+#include <errno.h>
 
 #include <isc/app.h>
 #include <isc/condition.h>