Use snprintf instead of sprintf for get_ssl_library_version

This is avoid a warning/error (when using -Werror) under current macOS
of sprintf:

   __deprecated_msg("This function is provided for compatibility
   reasons only.  Due to security concerns inherent in the design
   of sprintf(3), it is highly recommended that you use snprintf(3)
   instead.")

Change-Id: I3c6fd36eb9daee9244d6dc6d9f22de1c5cf9d039
Signed-off-by: Arne Schwabe <[email protected]>
Acked-by: Frank Lichtenheld <[email protected]>
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg28458.html
Signed-off-by: Gert Doering <[email protected]>
(cherry picked from commit 6a60d1b)

src/openvpn/ssl_mbedtls.c

@@ -1613,7 +1613,7 @@ get_ssl_library_version(void)
 {
     static char mbedtls_version[30];
     unsigned int pv = mbedtls_version_get_number();
-    sprintf( mbedtls_version, "mbed TLS %d.%d.%d",
+    snprintf(mbedtls_version, sizeof(mbedtls_version), "mbed TLS %d.%d.%d",
              (pv>>24)&0xff, (pv>>16)&0xff, (pv>>8)&0xff );
     return mbedtls_version;
 }