Fix warning with overridden virtual methods

Overridden virtual methods were not marked as such.

gcc/rust/ChangeLog:

	* ast/rust-pattern.h: Add override modifier to overriding methods.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
diff --git a/gcc/rust/ast/rust-pattern.h b/gcc/rust/ast/rust-pattern.h
index 4c072a1..68fee92 100644
--- a/gcc/rust/ast/rust-pattern.h
+++ b/gcc/rust/ast/rust-pattern.h
@@ -49,7 +49,7 @@
 
   void accept_vis (ASTVisitor &vis) override;
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
   Literal &get_literal () { return lit; }
 
@@ -147,7 +147,7 @@
   bool get_is_mut () const { return is_mut; }
   bool get_is_ref () const { return is_ref; }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -175,7 +175,7 @@
 
   void accept_vis (ASTVisitor &vis) override;
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -429,7 +429,7 @@
     return upper;
   }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -497,7 +497,7 @@
 
   bool get_is_mut () const { return is_mut; }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -932,7 +932,7 @@
   PathInExpression &get_path () { return path; }
   const PathInExpression &get_path () const { return path; }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -1169,7 +1169,7 @@
   PathInExpression &get_path () { return path; }
   const PathInExpression &get_path () const { return path; }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -1409,7 +1409,7 @@
     return items;
   }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -1469,7 +1469,7 @@
     return pattern_in_parens;
   }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -1533,7 +1533,7 @@
     return items;
   }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather
@@ -1598,7 +1598,7 @@
     return alts;
   }
 
-  NodeId get_node_id () const { return node_id; }
+  NodeId get_node_id () const override { return node_id; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather