C++: add explicit to Context constructor

Signed-off-by: Mislav Novakovic <mislav.novakovic@sartura.hr>
diff --git a/swig/cpp/src/Libyang.hpp b/swig/cpp/src/Libyang.hpp
index f3cf84a..44ef836 100644
--- a/swig/cpp/src/Libyang.hpp
+++ b/swig/cpp/src/Libyang.hpp
@@ -69,7 +69,7 @@
 {
 public:
     Context(struct ly_ctx *ctx, S_Deleter deleter);
-    Context(const char *search_dir = nullptr, int options = 0);
+    explicit Context(const char *search_dir = nullptr, int options = 0);
     Context(const char *search_dir, const char *path, LYD_FORMAT format, int options = 0);
     Context(const char *search_dir, LYD_FORMAT format, const char *data, int options = 0);
     ~Context();