deps/opts-parser: Add missing c extern for cpp

deps/opts-parser/opts-parser.h

@@ -2,6 +2,10 @@
 
 #include <stddef.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct obs_option {
 	char *name;
 	char *value;
@@ -17,3 +21,7 @@ struct obs_options {
 
 struct obs_options obs_parse_options(const char *options_string);
 void obs_free_options(struct obs_options options);
+
+#ifdef __cplusplus
+}
+#endif