Fix missing return statement ssl_server2 idling

Also, introduce MBEDTLS_EINTR locally in net_sockets.c
for the platform-dependent return code macro used by
the `select` call to indicate that the poll was interrupted
by a signal handler: On Unix, the corresponding macro is EINTR,
while on Windows, it's WSAEINTR.

library/net_sockets.c

@@ -45,6 +45,8 @@
 #if (defined(_WIN32) || defined(_WIN32_WCE)) && !defined(EFIX64) && \
     !defined(EFI32)
 
+#define MBEDTLS_EINTR WSAEINTR
+
 #ifdef _WIN32_WINNT
 #undef _WIN32_WINNT
 #endif
@@ -82,6 +84,8 @@ static int wsa_init_done = 0;
 #include <netdb.h>
 #include <errno.h>
 
+#define MBEDTLS_EINTR EINTR
+
 #endif /* ( _WIN32 || _WIN32_WCE ) && !EFIX64 && !EFI32 */
 
 /* Some MS functions want int and MSVC warns if we pass size_t,
@@ -475,12 +479,7 @@ int mbedtls_net_poll( mbedtls_net_context *ctx, uint32_t rw, uint32_t timeout )
         ret = select( fd + 1, &read_fds, &write_fds, NULL,
                       timeout == (uint32_t) -1 ? NULL : &tv );
     }
-#if ( defined(_WIN32) || defined(_WIN32_WCE) ) && !defined(EFIX64) && \
-    !defined(EFI32)
-    while( ret == WSAEINTR );
-#else
-    while( ret == EINTR );
-#endif
+    while( ret == MBEDTLS_EINTR );
 
     if( ret < 0 )
         return( MBEDTLS_ERR_NET_POLL_FAILED );

programs/ssl/ssl_client2.c

@@ -462,7 +462,7 @@ int idle( mbedtls_net_context *fd,
         poll_type = MBEDTLS_NET_POLL_READ;
 #if !defined(MBEDTLS_TIMING_C)
     else
-        return;
+        return( 0 );
 #endif
 
     while( 1 )

programs/ssl/ssl_server2.c

@@ -863,7 +863,7 @@ int idle( mbedtls_net_context *fd,
         poll_type = MBEDTLS_NET_POLL_READ;
 #if !defined(MBEDTLS_TIMING_C)
     else
-        return;
+        return( 0 );
 #endif
 
     while( 1 )