Only warn when the protocol version is not 2.x do not die.

This makes the program compatible with future protocol updates.
Before it was just dying so even if the new protocol was compatible
the program needed to be recompiled.

test/test-10.ok

-ERROR: Device protocol is 3.3 but this program supports 2.x only.
+WARNING: Device protocol is 3.3 but this program is tested with 2.x only.
+Device info
+  -------------------------------------------------------------------
+  | Device address             | sdi-matrix                         |
+  | Device port                | 9990                               |
+  | Model name                 | Blackmagic Micro Videohub          |
+  | Unique ID                  | 7c2e0d021714                       |
+  | Protocol                   | 3.3                                |
+  | Video inputs               | 16                                 |
+  | Video outputs              | 16                                 |
+  -------------------------------------------------------------------
+
+Video inputs
+  ----------------------------------------------------------------------
+  | ### | Video input name         | nn | Routed to output         | s |
+  ----------------------------------------------------------------------
+  |   1 |                          |  0 | -                        |   |
+  |   2 |                          |  0 | -                        |   |
+  |   3 |                          |  0 | -                        |   |
+  |   4 |                          |  0 | -                        |   |
+  |   5 |                          |  0 | -                        |   |
+  |   6 |                          |  0 | -                        |   |
+  |   7 |                          |  0 | -                        |   |
+  |   8 |                          |  0 | -                        |   |
+  |   9 |                          |  0 | -                        |   |
+  |  10 |                          |  0 | -                        |   |
+  |  11 |                          |  0 | -                        |   |
+  |  12 |                          |  0 | -                        |   |
+  |  13 |                          |  0 | -                        |   |
+  |  14 |                          |  0 | -                        |   |
+  |  15 |                          |  0 | -                        |   |
+  |  16 |                          |  0 | -                        |   |
+  ----------------------------------------------------------------------
+
+Video outputs
+  ---------------------------------------------------------------------
+  | ### | x | Video output name        | Connected video input    | s |
+  ---------------------------------------------------------------------
+  |   1 |   |                          |                          |   |
+  |   2 |   |                          |                          |   |
+  |   3 |   |                          |                          |   |
+  |   4 |   |                          |                          |   |
+  |   5 |   |                          |                          |   |
+  |   6 |   |                          |                          |   |
+  |   7 |   |                          |                          |   |
+  |   8 |   |                          |                          |   |
+  |   9 |   |                          |                          |   |
+  |  10 |   |                          |                          |   |
+  |  11 |   |                          |                          |   |
+  |  12 |   |                          |                          |   |
+  |  13 |   |                          |                          |   |
+  |  14 |   |                          |                          |   |
+  |  15 |   |                          |                          |   |
+  |  16 |   |                          |                          |   |
+  ---------------------------------------------------------------------
+

videohubctrl.c

 		die("The device does not respond correctly. Is it Videohub?");
 
 	if (strstr(data->device.protocol_ver, "2.") != data->device.protocol_ver)
-		die("Device protocol is %s but this program supports 2.x only.\n",
+		q("WARNING: Device protocol is %s but this program is tested with 2.x only.\n",
 			data->device.protocol_ver);
 
 	if (!data->device.dev_present) {