Fix indentation of m_language declaration

Author: mcbarton

include/xeus-cpp/xinterpreter.hpp

@@ -79,7 +79,7 @@ namespace xcpp
 
         std::string m_version;
 
-	std::string m_language;
+	    std::string m_language;
 
         xmagics_manager xmagics;
         xpreamble_manager preamble_manager;