vdisp,vcap/decklink: do not fail if insuff drv ver

The motivation is to allow (although not recommend) running even with
old drivers - it will usually work and just the DeckLink IP features
won't be available (and warnings about that).

+ print it again at the beginning (== print also when :help requested)
+ change the message not_inst-or-outdated jus to outdated because in that
place it is obvious that the drivers are present

src/blackmagic_common.cpp

@@ -238,7 +238,7 @@ bool blackmagic_api_version_check()
         }
 
         if (BLACKMAGIC_DECKLINK_API_VERSION > value) { // this is safe comparision, for internal structure please see SDK documentation
-                log_msg(LOG_LEVEL_ERROR, "The DeckLink drivers may not be installed or are outdated.\n");
+                log_msg(LOG_LEVEL_ERROR, "The DeckLink drivers are be outdated.\n");
                 log_msg(LOG_LEVEL_ERROR, "You should have at least the version UltraGrid has been linked with.\n");
                 log_msg(LOG_LEVEL_ERROR, "Vendor download page is http://www.blackmagic-design.com/support\n");
                 print_decklink_version();

src/video_capture/decklink.cpp

@@ -1426,6 +1426,8 @@ vidcap_decklink_init(struct vidcap_params *params, void **state)
 {
         const char *fmt = vidcap_params_get_fmt(params);
 
+        blackmagic_api_version_check();
+
         if (strcmp(fmt, "help") == 0 || strcmp(fmt, "fullhelp") == 0) {
                 decklink_help(strcmp(fmt, "fullhelp") == 0);
                 return VIDCAP_INIT_NOERR;
@@ -1459,11 +1461,6 @@ vidcap_decklink_init(struct vidcap_params *params, void **state)
 		return VIDCAP_INIT_FAIL;
 	}
 
-        if (!blackmagic_api_version_check()) {
-                delete s;
-                return VIDCAP_INIT_FAIL;
-        }
-
         switch (get_bits_per_component(s->codec)) {
         case 0: s->requested_bit_depth = 0; break;
         case 8: s->requested_bit_depth = bmdDetectedVideoInput8BitDepth; break;

src/video_display/decklink.cpp

@@ -1416,6 +1416,8 @@ static void *display_decklink_init(struct module *parent, const char *fmt, unsig
         IDeckLinkConfiguration*         deckLinkConfiguration = NULL;
         // for Decklink Studio which has switchable XLR - analog 3 and 4 or AES/EBU 3,4 and 5,6
 
+        blackmagic_api_version_check();
+
         if (strcmp(fmt, "help") == 0 || strcmp(fmt, "fullhelp") == 0) {
                 show_help(strcmp(fmt, "fullhelp") == 0);
                 return INIT_NOERR;
@@ -1444,11 +1446,6 @@ static void *display_decklink_init(struct module *parent, const char *fmt, unsig
                 return NULL;
         }
 
-        if (!blackmagic_api_version_check()) {
-                delete s;
-                return NULL;
-        }
-
         // Connect to the first DeckLink instance
         for (auto &d : bmd_get_sorted_devices(&s->com_initialized, true)) {
                 s->deckLink = get<0>(d).release(); // unmanage