Fix build failure due to missing 'smallint' definition

by adding <unistd.h> header file.

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

libc/inet/getnetbyad.c

@@ -18,6 +18,7 @@
 #define __FORCE_GLIBC
 #include <features.h>
 #include <netdb.h>
+#include <unistd.h>
 
 libc_hidden_proto(setnetent)
 libc_hidden_proto(getnetent)

libc/inet/getnetbynm.c

@@ -19,6 +19,7 @@
 #include <features.h>
 #include <netdb.h>
 #include <string.h>
+#include <unistd.h>
 
 /* Experimentally off - libc_hidden_proto(strcmp) */
 libc_hidden_proto(setnetent)

libc/inet/getnetent.c

@@ -22,6 +22,7 @@
 #include <malloc.h>
 #include <netdb.h>
 #include <arpa/inet.h>
+#include <unistd.h>
 
 libc_hidden_proto(fopen)
 libc_hidden_proto(fclose)

libc/inet/getproto.c

@@ -61,6 +61,7 @@
 #include <string.h>
 #include <malloc.h>
 #include <errno.h>
+#include <unistd.h>
 
 libc_hidden_proto(fopen)
 /* Experimentally off - libc_hidden_proto(strcmp) */

libc/inet/getservice.c

@@ -63,6 +63,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <errno.h>
+#include <unistd.h>
 
 /* Experimentally off - libc_hidden_proto(strcmp) */
 /* Experimentally off - libc_hidden_proto(strpbrk) */

libc/inet/resolv.c

@@ -1061,7 +1061,6 @@ void attribute_hidden __open_nameservers(void)
 #define RESOLV_ARGS 5
 	char szBuffer[128], *p, *argv[RESOLV_ARGS];
 	int argc;
-	/* int rv = 0; */
 
 	__UCLIBC_MUTEX_LOCK(__resolv_lock);
 	if (__nameservers > 0)