mod_spandsp_dsp.c: resolve V.18 mode and v18_init compilation errors

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Commit that Introduced Compilation Error :

freeswitch/spandsp@d9681c3#diff-348092e97708aedff108326c3f98a9ea907ee9a58b5a780e508d5f08503475fb

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Resolve compilation errors in `mod_spandsp_dsp.c` caused by SpanDSP API updates:
1. **Mode Constants**: Updated deprecated mode names (e.g., `V18_MODE_5BIT_4545` → `V18_MODE_WEITBRECHT_5BIT_4545`).
2. **v18_init Calls**: Added missing `status_handler` and `status_handler_user_data` arguments (set to `NULL`).

These changes align mod_spandsp_dsp.c with the SpanDSP library’s API defined in v18.h.

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Explanation :

    - The mode constants in mod_spandsp_dsp.c (e.g., V18_MODE_5BIT_4545) are outdated. SpanDSP's v18.h uses newer names like V18_MODE_WEITBRECHT_5BIT_4545,

    - The v18_init function now requires 8 arguments (as per v18.h), but the code only passes 6.Add two NULL arguments for the missing parameters (status_handler and status_handler_user_data).
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for ref. Errors were:

mod_spandsp_dsp.c: In function 'get_v18_mode':
mod_spandsp_dsp.c:159:17: error: 'V18_MODE_5BIT_4545' undeclared (first use in this function)
  159 |         int r = V18_MODE_5BIT_4545;
      |                 ^~~~~~~~~~~~~~~~~~
mod_spandsp_dsp.c:159:17: note: each undeclared identifier is reported only once for each function it appears in
mod_spandsp_dsp.c:165:29: error: 'V18_MODE_5BIT_50' undeclared (first use in this function)
  165 |                         r = V18_MODE_5BIT_50;
      |                             ^~~~~~~~~~~~~~~~
mod_spandsp_dsp.c: In function 'spandsp_tdd_send_session':
mod_spandsp_dsp.c:216:21: error: too few arguments to function 'v18_init'
  216 |         tdd_state = v18_init(NULL, TRUE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, NULL);
      |                     ^~~~~~~~
In file included from /usr/local/include/spandsp.h:114,
                 from mod_spandsp.h:50,
                 from mod_spandsp_dsp.c:36:
/usr/local/include/spandsp/v18.h:138:29: note: declared here
  138 | SPAN_DECLARE(v18_state_t *) v18_init(v18_state_t *s,
      |                             ^~~~~~~~
mod_spandsp_dsp.c: In function 'spandsp_tdd_encode_session':
mod_spandsp_dsp.c:263:26: error: too few arguments to function 'v18_init'
  263 |         pvt->tdd_state = v18_init(NULL, TRUE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, NULL);
      |                          ^~~~~~~~
/usr/local/include/spandsp/v18.h:138:29: note: declared here
  138 | SPAN_DECLARE(v18_state_t *) v18_init(v18_state_t *s,
      |                             ^~~~~~~~
mod_spandsp_dsp.c: In function 'spandsp_tdd_decode_session':
mod_spandsp_dsp.c:341:26: error: too few arguments to function 'v18_init'
  341 |         pvt->tdd_state = v18_init(NULL, FALSE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, pvt);
      |                          ^~~~~~~~
/usr/local/include/spandsp/v18.h:138:29: note: declared here
  138 | SPAN_DECLARE(v18_state_t *) v18_init(v18_state_t *s,
      |                             ^~~~~~~~
make[4]: *** [Makefile:772: mod_spandsp_la-mod_spandsp_dsp.lo] Error 1

src/mod/applications/mod_spandsp/mod_spandsp_dsp.c

@@ -156,13 +156,13 @@ static int get_v18_mode(switch_core_session_t *session)
 {
 	switch_channel_t *channel = switch_core_session_get_channel(session);
 	const char *var;
-	int r = V18_MODE_5BIT_4545;
+	int r = V18_MODE_WEITBRECHT_5BIT_4545;
 
 	if ((var = switch_channel_get_variable(channel, "v18_mode"))) {
 		if (!strcasecmp(var, "5BIT_45") || !strcasecmp(var, "baudot")) {
-			r = V18_MODE_5BIT_4545;
+			r = V18_MODE_WEITBRECHT_5BIT_4545;
 		} else if (!strcasecmp(var, "5BIT_50")) {
-			r = V18_MODE_5BIT_50;
+			r = V18_MODE_WEITBRECHT_5BIT_50;
 		} else if (!strcasecmp(var, "DTMF")) {
 			r = V18_MODE_DTMF;
 		} else if (!strcasecmp(var, "EDT")) {
@@ -213,7 +213,7 @@ switch_status_t spandsp_tdd_send_session(switch_core_session_t *session, const c
 		return SWITCH_STATUS_FALSE;
 	}
 
-	tdd_state = v18_init(NULL, TRUE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, NULL);
+	tdd_state = v18_init(NULL, TRUE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, NULL, NULL, NULL);
 
 
 	v18_put(tdd_state, text, -1);
@@ -260,7 +260,7 @@ switch_status_t spandsp_tdd_encode_session(switch_core_session_t *session, const
 	}
 
 	pvt->session = session;
-	pvt->tdd_state = v18_init(NULL, TRUE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, NULL);
+	pvt->tdd_state = v18_init(NULL, TRUE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, NULL, NULL, NULL);
 	pvt->head_lead = TDD_LEAD;
 
 	v18_put(pvt->tdd_state, text, -1);
@@ -338,7 +338,7 @@ switch_status_t spandsp_tdd_decode_session(switch_core_session_t *session)
 	}
 
 	pvt->session = session;
-	pvt->tdd_state = v18_init(NULL, FALSE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, pvt);
+	pvt->tdd_state = v18_init(NULL, FALSE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, pvt, NULL, NULL);
 
 	if ((status = switch_core_media_bug_add(session, "spandsp_tdd_decode", NULL,
 						tdd_decode_callback, pvt, 0, SMBF_READ_REPLACE | SMBF_NO_PAUSE, &bug)) != SWITCH_STATUS_SUCCESS) {