string: add snprintf

Signed-off-by: Simon Rozman <simon@rozman.si>

UnitTests/main.cpp

@@ -28,6 +28,7 @@ int main(int, const char *[])
 		UnitTests::stream::replicator();
 		UnitTests::string::strncpy();
 		UnitTests::string::sprintf();
+		UnitTests::string::snprintf();
 		UnitTests::unicode::charset_encoder();
 		UnitTests::unicode::normalize();
 		UnitTests::unicode::str2wstr();