various: Fix GCC 11.2 compilation issues.

* Initialize some variables that are never used anyway.

* Use valid pointers instead of integers cast to void pointers when
  calling pthread_setspecific().

ASTERISK-29711 #close
ASTERISK-29713 #close

Change-Id: I8728cd6f2f4b28e0e48113c5da450b768c2a6683

main/channel.c

@@ -10344,7 +10344,7 @@ static void channel_set_intercept_mode(int in_intercept_mode)
 	int status;
 
 	status = ast_threadstorage_set_ptr(&in_intercept_routine,
-		in_intercept_mode ? (void *) 1 : (void *) 0);
+		in_intercept_mode ? &(int) { 1 } : NULL);
 	if (status) {
 		ast_log(LOG_ERROR, "Failed to set dialplan intercept mode\n");
 	}

main/logger.c

@@ -2213,7 +2213,7 @@ void ast_log_safe(int level, const char *file, int line, const char *function, c
 		return;
 	}
 
-	if (ast_threadstorage_set_ptr(&in_safe_log, (void*)1)) {
+	if (ast_threadstorage_set_ptr(&in_safe_log, &(int) { 1 })) {
 		/* We've failed to set the flag that protects against
 		 * recursion, so bail. */
 		return;

utils/extconf.c

@@ -2863,8 +2863,8 @@ static struct ast_config *ast_config_internal_load(const char *filename, struct
 
 static struct ast_config *ast_config_internal_load(const char *filename, struct ast_config *cfg, int withcomments, const char *suggested_incl_file)
 {
-	char db[256];
-	char table[256];
+	char db[256] = "";
+	char table[256] = "";
 	struct ast_config_engine *loader = &text_file_engine;
 	struct ast_config *result;