Removed shared_ptr shim

Since C++17 is now the default mosh version, remove the shared_ptr
shim in favor of std::shared_ptr.

src/terminal/parsertransition.h

@@ -58,14 +58,14 @@ namespace Parser {
 
       return *this;
     }
-    Transition( ActionPointer s_action=shared::make_shared< Ignore >(), State *s_next_state=NULL )
+    Transition( ActionPointer s_action = std::make_shared<Ignore>(), State *s_next_state=NULL )
       : action( s_action ), next_state( s_next_state )
     {}
 
     // This is only ever used in the 1-argument form;
     // we use this instead of an initializer to
     // tell Coverity the object never owns *action.
-    Transition( State *s_next_state, ActionPointer s_action=shared::make_shared< Ignore >() )
+    Transition( State *s_next_state, ActionPointer s_action = std::make_shared<Ignore>() )
       : action( s_action ), next_state( s_next_state )
     {}
   };