libobs/plugins/UI: Suppress -Wimplicit-fallthrough introduced by GCC 7

Signed-off-by: Shaolin <admshao@gmail.com>

libobs/graphics/effect-parser.c

@@ -228,12 +228,14 @@ static void ep_parse_struct(struct effect_parser *ep)
 
 		case PARSE_UNEXPECTED_CONTINUE:
 			cf_adderror_syntax_error(&ep->cfp);
+			/* Falls through. */
 		case PARSE_CONTINUE:
 			ep_var_free(&var);
 			continue;
 
 		case PARSE_UNEXPECTED_BREAK:
 			cf_adderror_syntax_error(&ep->cfp);
+			/* Falls through. */
 		case PARSE_BREAK:
 			ep_var_free(&var);
 			do_break = true;

libobs/graphics/shader-parser.c

@@ -277,12 +277,14 @@ static void sp_parse_struct(struct shader_parser *sp)
 
 		case PARSE_UNEXPECTED_CONTINUE:
 			cf_adderror_syntax_error(&sp->cfp);
+			/* Falls through. */
 		case PARSE_CONTINUE:
 			shader_var_free(&var);
 			continue;
 
 		case PARSE_UNEXPECTED_BREAK:
 			cf_adderror_syntax_error(&sp->cfp);
+			/* Falls through. */
 		case PARSE_BREAK:
 			shader_var_free(&var);
 			do_break = true;

libobs/util/cf-lexer.c

@@ -123,6 +123,7 @@ static bool cf_is_token_break(struct base_token *start_token,
 			start_token->type = BASETOKEN_DIGIT;
 			break;
 		}
+		/* Falls through. */
 
 	case BASETOKEN_NONE:
 		return true;